JP3697934B2 - Fuel property detection device and engine fuel supply control device - Google Patents

Description

ただし、Ｔsample：サンプル周期（空燃比をサンプリングする周期）、
Ｔ₁ ：低周波成分の時定数、
Ｔ₂ ：高周波成分の時定数、
ｋ₁ ：低周波成分のゲイン、
ｋ₂ ：高周波成分のゲイン、
Ａ₁ ：ｅ^-Tsample/T1、
Ａ₂ ：ｅ^-Tsample/T2、
Ｂ₁ ：ｋ₁、
Ｂ₂ ：ｋ₂、
数２式において、１番目の式（連続値系）を離散値系に変換したものが２番目の式、この２番目の式にｚ＝ｅ^sTsampleを代入して整理したものが３番目の式である。また、３番目の式をブロック図で示したのが図５である。
【０１０７】
なお、燃料挙動に伴う無駄時間については燃料挙動の数学モデルに取り込まず、出力信号を時系列的にオフセットさせることで、モデル次数の上昇を抑える（詳細は１．３で後述する）。
【０１０８】
１．２排気モデル
排気モデルは、図６のように各気筒毎の排気ダイナミクス、排気マニフォールド集合部におけるガス混合ダイナミクス、センサ特性の３要素から構成されると考える。これらを総合すると、「無駄時間＋遅れ系」の物理モデルで表すことができる。遅れ系としては、排気ガス輸送遅れ＋ガス混合遅れ＋センサ応答遅れが考えられ、それぞれが１次遅れ以上のモデルである。ただし、今回はオンボードで（ＥＣＭ２上で）プラントモデルを同定することを考えると、なるべく高次となることを避ける必要があり、排気モデルとして１つの時定数で代表し、次のように１次遅れ系の数学モデルで記述する。
【０１０９】
【数３】
Ｇ_ex(ｓ)＝１／(ｓＴ_ex＋１)
Ｇ_ex(ｚ)＝(１−ｅ^-Tsample/Tex)／(ｚ−ｅ^-Tsample/Tex)
Ｇ_ex(ｚ)＝(１−Ａ₃)／(ｚ−Ａ₃)
ただし、Ｇ_ex ：排気動特性の伝達関数、
Ｔ_ex ：蒸発時定数、
Ｔsample：サンプル周期、
Ａ₃ ：ｅ^-Tsample/Tex、
数３式においても、１番目の式を離散値系に変換したものが２番目の式、２番目の式にｚ＝ｅ^sTsampleを代入して整理したものが３番目の式である。
【０１１０】
また、無駄時間については、燃料挙動モデルと同様に時系列的にオフセットさせることとし、排気モデルに取り込まない（１．３で後述する）。
【０１１１】
１．３無駄時間モデル
本プラントモデル３１は、入力に実噴射パルス幅ＣＴＩｎ、出力にＡ／Ｆセンサ３出力電圧読み込み値とおいているため、図３に示したように、実噴射パルス幅ＣＴＩｎを演算してからＡ／Ｆセンサ出力値をＥＣＭ２が読み込むまでにはいくつかの無駄時間（図では「Delay」で表示）が存在する。そこで、改めて入出力間の無駄時間を図７に詳細に示す。
【０１１２】
ここで、各無駄時間を説明する。
【０１１３】
１）Delay１：噴射量演算から実噴射タイミングまでのディレイ、
実噴射パルス幅ＣＴＩｎは１０ｍｓ毎に演算しており、実際に燃料を噴射するタイミングまでは必ずしも毎サイクル同一ではない。そこで演算された噴射タイミング（燃料噴き始め）角度とそのときの回転数より、パルス幅演算タイミングからの時間を算出することにより無駄時間Delay１を求める。
【０１１４】
２）Delay２：実噴射タイミングからＩＶＯ（吸気弁開）までのディレイ、
これは、燃料を噴射し、吸気弁が開いて燃料がシリンダに吸入されるまでの時間である。本ディレイは燃料挙動特性により決まり、各運転条件および燃料性状によって設定する。たとえば市販されている燃料のうち揮発性がほぼ中間の燃料を用いて、各運転条件（たとえば、エンジン回転数と負荷）毎に燃料をステップ的に変化させて実際に応答時間を計測しながら適切な値を設定する。
【０１１５】
３）Delay３：ＩＶＯからＥＶＯ（排気弁開）まで（吸入→圧縮→燃焼→排気）のディレイ、
これは、燃料が吸気弁よりシリンダ内に吸入され、燃焼ガスが排気弁から排出されるまでの時間である。このディレイは回転数およびカムプロフィールから求めることができ、設計仕様より求められる。
【０１１６】
４）Delay４：燃焼ガスが排気弁を出てからＡ／Ｆセンサに到達するまでのディレイ、
これは、シリンダ内の燃焼ガスが排気弁より排出されてから排気管を通りＡ／Ｆセンサ部に到達するまでの時間である。排気の流速（回転数、負荷等に依存）と排気長さ、Ａ／Ｆセンサ取り付け位置等によって設定する。なお、計算が複雑になるが、運転条件およびハードスペックから求めてもよい。
【０１１７】
５）Delay５：センサ応答ディレイ、
これは、Ａ／Ｆセンサ部にガスが到達してからＡ／Ｆセンサが電圧を出力するまでの時間である。Ａ／Ｆセンサ自体は酸素量が変動すると、数ｍｓで反応するが、センサカバーによるガス混合遅れが支配的であり、その時間はセンサカバーの形状により大きく異なる。このため、本ディレイはDelay４と同様にして適切な値を設定する。
【０１１８】
６）Delay６：センサ出力値をＡ／Ｄ変換しＥＣＭ２に取り込むまでのディレイ、
これは、Ａ／Ｆセンサが出力する電圧をＥＣＭ２に取り込むためにＡ／Ｄ変換を行うことによるディレイである。現在のハード構成ではＡ／Ｆセンサ３のＡ／Ｄ変換は２ｍｓ毎に行っており、最大無駄時間は２ｍｓである。
【０１１９】
７）Delay７：センサ出力値をメモリにバッファリングするまでのディレイ、
Ａ／Ｆセンサ出力値を１０ｍｓでサンプリングする場合に、サンプリングタイミングによっては最大１０ｍｓの無駄時間が生じるおそれがある。このため２ｍｓでＡ／Ｄ変換した値より算出した応答開始からサンプリングタイミングまでの無駄時間をDelay７として算出する。
【０１２０】
８）Delay８：バラツキ分、
これは、Delay１〜７より求めた無駄時間以外に生じるバラツキ分である。機種間バラツキや適合のバラツキ等が考えられ、運転毎にも不確定であるため、Delay１〜７経過後の空燃比信号の立ち上がりを判定し決定する。
【０１２１】
これで、各無駄時間の説明を終える。
【０１２２】
上記のDelay１〜８を分析すると、無駄時間は
▲１▼運転条件により決定する項、
▲２▼演算タイミングより決定する事項、
▲３▼燃料性状等により変動する項
に分類することができる（図８参照）。よって、実際の無駄時間は、次の式で表すことができる。
【０１２３】
無駄時間
＝適合項（運転条件により決定、テーブルやマップの検索）
＋演算項（演算タイミングより決定、タイミング信号を等を用いて演算）
＋判定項（燃料性状等のバラツキ等により変動するため、随時判定する）
２．プラントモデルの同定
２．１同定するモデルの作成
実際のエンジンは強い非線形性を有するが、本制御では、ある動作点近傍では線形でありかつ時不変である、いわゆる線形時不変システム（ＬＴＩ：Linear Time-Invariant System）であると仮定する。
【０１２４】
また、離散時間系ＬＴＩシステムを、Ｚ領域ではなく時間領域で入出力を記述するため、シフトオペレータｑ^-1を以下のように定義する。
【０１２５】
【数４】
ｑ^-1ｘ(ｋ)＝ｘ(ｋ−１)
ただし、離散時間＝ｋＴ（Ｔ：サンプリング周期、ｋ＝０，１，２，・・・）である。
【０１２６】
これを用いて、離散値系の入力ｕ(ｔ)、出力ｙ(ｔ)のシステム伝達関数を記述すると、
【０１２７】
【数５】
ｙ(ｋ)＝Ｇ(ｑ，θ)・ｕ(ｋ)
となる。θはモデルを記述するパラメータにより構成される。しかし、これは理想的な入出力であり、外部からの雑音を考慮すると、
【０１２８】
【数６】
ｙ(ｋ)＝Ｇ(ｑ，θ)・ｕ(ｋ)＋Ｈ(ｑ，θ)・ｗ(ｋ)
と記述できる。ここで、Ｈ(ｑ，θ)は雑音モデルであり、一般的な離散時間系ＬＴＩシステムは、数６式で表すことができる。同システムのブロック図は図９である。
【０１２９】
ここで、同システムの伝達関数Ｇ(ｑ)は、数２式の３番目の式と数３式の３番目の式の積であり、さらにＺ^-1で記述されたものをシフトオペレータｑ^-1で記述したものとなって、
【０１３０】
【数７】

と表せる。このシステムの伝達関数Ｇ(ｑ)を、
【０１３１】
【数８】
Ｇ(ｑ，θ)＝Ｂ(ｑ，θ)／Ａ(ｑ，θ)
の式で定義すると、システムの出力値ｙ(ｋ)は、
【０１３２】
【数９】
ｙ(ｋ，θ)＝｛Ｂ(ｑ，θ)／Ａ(ｑ，θ)｝・ｕ(ｋ)＋Ｈ(ｑ，θ)・ｗ(ｋ)
と表すことができる。このように、同定するモデルとしては、プラントモデルであるＧ(ｑ)と、雑音モデルであるＨ(ｑ)を適切な形としたものとを組み合わせたものを採用する。
【０１３３】
２．２同定手法
数６式で定義した離散時間系ＬＴＩシステムにおいて、時刻(ｋ−１)までに測定された入出力データに基づいた出力ｙ(ｋ)の一段先予測値ｙ(ｋ｜θ)は、
【０１３４】
【数１０】
ｙ(ｋ｜θ)＝［１−Ｈ^-1(ｑ，θ)］ｙ(ｋ)＋Ｈ^-1(ｑ，θ)Ｇ(ｑ，θ)ｕ(ｋ)
の式で表される。これにより、時刻ｋにおける出力を(ｋ−１)までに取得したデータで記述することができる。
【０１３５】
予測誤差ε(ｋ｜θ)は
【０１３６】
【数１１】
ε(ｋ｜θ)＝ｙ(ｋ)−ｙ(ｋ｜θ)
の式で表すことができる。
【０１３７】
さて、パラメータ推定のための評価規範Ｊ_N(θ)として、
【０１３８】
【数１２】

を設定する。ここで、関数ｌ(ｋ，θ，ε(ｋ，θ))は予測誤差ε(ｋ，θ)の大きさを測る任意のスカラ値関数であり、どのようなノルムを選択するかは、同定結果の利用目的に依存する（２乗ノルムや対数尤度など）。このような評価規範を定義することによって、未知パラメータθの推定値（θ(Ｎ)とする）が決定される。つまり、
【０１３９】
【数１３】

となるθを求めることである。
【０１４０】
一般的に同定手法には様々な手法が提案されているが、エンジンのようなものは間欠的なイベント（燃焼サイクル等）であり、非常に非線形性が強い制御対象である。しかしながら、本制御ではアルゴリズムの簡略化のため、動作点周りでは線形時不変（ＬＴＩ）システムであると仮定している。
【０１４１】
今回は演算量の少なさ、同定精度、対外乱性能を考慮し、線形モデルの同定手法の代表的なものである「パラメトリックモデル同定であるＡＲＸモデルを用いた一括同定手法」を採用する。
【０１４２】
２．３ＡＲＸモデルの同定手法
ＡＲＸモデルは式誤差モデルと呼ばれ、次のように差分方程式の右辺に外乱項ｅ(ｋ)（ＡＲＸモデルでは白色雑音として仮定しており、ｗ(ｋ)とする）が入っている。
【０１４３】
【数１４】

モデルを記述するパラメータベクトルθは、
【０１４４】
【数１５】
θ＝［ａ₁，・・・，ａ_na，ｂ₁，・・・，ｂ_nb］^T
となる。データベクトル（回帰ベクトル）ψ(ｋ)を、
【０１４５】
【数１６】
ψ(ｋ)＝［−ｙ(ｋ−１)，・・・，−ｙ(ｋ−ｎａ)，ｕ(ｋ−１)，・・・，ｕ(ｋ−ｎｂ)］^T
と定義すると、出力ｙ(ｋ)は次式のように表現できる。
【０１４６】
【数１７】
ｙ(ｋ)＝θ^Tψ(ｋ)＋ｗ(ｋ)
ＡＲＸモデルの一段先予測値ｙ(ｋ｜θ)は、数１０式より求めると、θに関して線形であり、
【０１４７】
【数１８】
ｙ(ｋ｜θ)＝θ^Tψ(ｋ)
と表される。このときの予測誤差ε(ｋ，θ)は、
【０１４８】
【数１９】
ε(ｋ，θ)＝ｙ(ｋ)−θ^Tψ(ｋ)
と表わすことができる。この線形回帰モデルに対して最小２乗法を適用すると、スカラ値関数ｌ(ｋ，θ，ε(ｋ，θ))は、
【０１４９】
【数２０】
ｌ(ｋ，θ，ε(ｋ，θ))＝ε²(ｋ，θ)
となり、パラメータ推定の評価規範Ｊ_N(θ)は、
【０１５０】
【数２１】

となる。数２１式をさらに計算すると、
【０１５１】
【数２２】

【０１５２】
【数２３】
Ｊ_N(θ)＝ｃ(Ｎ)−２θ^Tｆ(Ｎ)＋θ^TＲ(Ｎ)θ
とおくことができる。
【０１５３】
ただし、数２３式のｃ(Ｎ)、ｆ(Ｎ)、Ｒ(Ｎ)は次の通りである。
【０１５４】
【数２４】

【０１５５】
【数２５】

【０１５６】
【数２６】

評価規範Ｊ_N(θ)が最小となるのは、Ｊ_N(θ)がθに関する二次関数であるため、最高次の係数が正であれば、Ｊ_N(θ)の微分値がゼロとなるところである。数２３式の微分値＝０とすると、次の正規方程式（θに関する連立一次方程式）が得られる。
【０１５７】
【数２７】

これより、Ｒ(Ｎ)が正定値行列であれば、Ｊ_N(θ)は微分値がゼロのとき最小となり（Ｊ_N(θ)は下に凸の関数、図１０参照）、
【０１５８】
【数２８】

の式によりパラメータθ(Ｎ)を推定することができる。以上の同定手順を図１１に示す。
【０１５９】
なお、上記の正定値行列の条件には次の３つがある。
【０１６０】
１）同定対象がｎ次の場合は、入力信号ｕ(ｋ)はｎ個以上の正弦波を含んでいなければならない（ステップ入力信号に十分な周波数成分を含ませる）。
【０１６１】
２）同定対象は安定である（エンジンは定常では安定系と考えて差し支えない）。
【０１６２】
３）同定対象は可観測である。すなわち、Ａ(ｑ，θ)とＢ(ｑ，θ)は共通因子を持たない（本モデルは離散系であるためＢ(ｑ，θ)のほうが次数が高いが問題なし）。
【０１６３】
２．４実際のＡＲＸモデルの同定
本モデルは、数７式より分母３次、分子３次の離散系モデルであり、
【０１６４】
【数２９】
Ａ(ｑ)＝１＋ａ₁・ｑ^-1＋ａ₂・ｑ^-2＋ａ₃・ｑ^-3
【０１６５】
【数３０】
Ｂ(ｑ)＝ｂ₁・ｑ^-1＋ｂ₂・ｑ^-2＋ｂ₃・ｑ^-3
と表すことができる。よってパラメータベクトルθおよびデータベクトルψ(ｋ)は、以下のように表すことができる。
【０１６６】
【数３１】
θ＝［ａ₁，ａ₂，ａ₃，ｂ₁，ｂ₂，ｂ₃］^T
【０１６７】
【数３２】
ψ(ｋ)＝［−ｙ(ｋ−１)，−ｙ(ｋ−２)，−ｙ(ｋ−３)，ｕ(ｋ−１)，ｕ(ｋ−２)，ｕ(ｋ−３)］^T
エンジン回転数が1200rpm時のサンプリング総数ＮをＮ＝128（1280ｍｓ）とすると、数２４式〜数２６式は、
【０１６８】
【数３３】

【０１６９】
【数３４】

【０１７０】
【数３５】

と表すことができる。
【０１７１】
２．５プラントモデル同定に必要な入力信号
システムの同定を行うためには、入力信号が、対象のもつ全てのモードを励起している必要がある。つまり、入力信号が多数の周波数成分を含んでいる必要がある。システムの同定においては、理想的には白色性入力が望ましいが、実際には疑似白色２値信号（Ｍ系列）が用いられる。しかし、エンジンの壁流応答のようなものでは、有効な周波数帯域は非常に低いところであり（応答が遅い）、Ｍ系列のような入力を加えてもほとんど応答波形を得ることができない。そこで、ステップ入力を与えることにより得られる波形（図１２参照）をもとに、システムを同定する。なお、ステップ入力のラプラス変換は１／ｓであるので、周波数ゲインは周波数に対して反比例で減少するため、パワースペクトルより有効な周波数域を決めておく必要がある。
【０１７２】
２．６実験結果
このようにして求めたパラメータθを用いれば、システムの伝達関数Ｇ(ｑ，θ)が定まるので、同定結果と実データを重ねたボード線図を図１３に示す（燃料性状が軽質であるほどカットオフ周波数が高くなる傾向がある）。実験結果によれば、吸気ポートに設けたスワールコントロールバルブが開状態、エンジン回転数が1200rpm近傍、冷却水温が４０℃近傍かつ低負荷域において±３σで燃料性状の異なる２つのガソリンを分離することができた。
【０１７３】
これで、項分け説明を終える。
【０１７４】
次に、ＥＣＭ２で実行される制御内容を、フローチャートにしたがって説明する。
【０１７５】
図１４は燃料性状を推定するためのもので、一定時間毎（１０ｍｓ毎）に実行する。ここでは、図１４をメインルーチン、図１５、図１６を図１４のサブルーチンとして構成しており、したがって、以下ではメインルーチンの説明途中でサブルーチンのあるステップになると、サブルーチンを説明する。
【０１７６】
図１４においてステップ１では燃料性状判定済みフラグをみる。まだ燃料性状を判定していないときは、ステップ２以降に進む。
【０１７７】
ステップ２〜６は排気空燃比（出力データ）をサンプリングする部分である。ステップ２では、Ａ／Ｆセンサ３で検出される空燃比を読み込み、ステップ３でこの空燃比の読み込み数（サンプリング数）Ｓ１とサンプリング総数Ｎ（たとえば128）を比較する。Ｓ１≦Ｎであるときは、ステップ４に進んで、空燃比をバッファリングして今回の処理を終了する。Ｓ１＞Ｎとなる前はステップ２、４の処理を繰り返す。
【０１７８】
Ｓ１＞Ｎとなったタイミングでステップ３よりステップ５に進む。このとき、バッファにはＮ個の出力データが格納されている。たとえば、今回値をｙ(１)に、前回値をｙ(２)に、２回前の値をｙ(３)に、・・・、Ｎ−１回前の値をｙ(Ｎ)にというようにして、合計でＮ個の出力データが格納されている。
【０１７９】
ステップ５、６ではＮ回前の出力データをバッファから捨て、今回読み込んだ空燃比をバッファリングする。つまり、今回値をｙ(１)に格納する。なお、過去の出力データは１回ずつ古い側にシフトして格納されることはいうまでもない。
【０１８０】
図示しないが、ステップ応答時の実噴射パルス幅ＣＴＩｎ（入力データ）も、今回値をｕ(１)に、前回値をｕ(２)に、２回前の値をｕ(３)に、・・・、Ｎ−１回前の値をｕ(Ｎ)にというようにして合計でＮ個の入力データが格納されており、これらの入力データと上記の出力データとは前述した遅れ時間を考慮して対応付けられる。
【０１８１】
ステップ７は燃料性状の推定を許可するかどうかを判定する部分である。このための具体的な内容は図４０、図４１に示す。燃料性状推定の許可判定は図４０、図４１のステップ１２１〜１３５の内容を一つずつチェックすることにより行い、各項目のすべてが満たされたときに燃料性状の推定を許可し、一つでも反するときは燃料性状の推定を禁止する。すなわち、
Ａ）パージ禁止中かつパージ禁止よりディレイ期間DELAY1#が経過している （ステップ１２１、１２２）、
Ｂ）ブレーキスイッチがＯＦＦ状態でありかつブレーキスイッチがＯＦＦ状態となってよりディレイ期間DELAY2#が経過している（ステップ１２３、１ ２４）、
Ｃ）気筒分配安定域かつ気筒分配安定域になってよりディレイ期間DELAY3# が経過している（ステップ１２５、１２６）、
Ｄ）失火判定されておらずかつ失火判定が解除されてよりディレイ期間DELA Y4#が経過している（ステップ１２７、１２８）、
Ｅ）ＥＧＲ（排気再循環）の禁止中かつＥＧＲ禁止よりディレイ期間DELAY5 #が経過している（ステップ１２９、１３０）、
Ｆ）スワールコントロールバルブを閉状態または開状態に切換えてよりディレイ期間DELAY6#が経過している（ステップ１３１）、
Ｇ）ロックアップ中かつロックアップしてよりディレイ期間DELAY7#が経過 している（ステップ１３２、１３３）、
Ｈ）燃料カット中でなくかつ燃料カットリカバーしてよりディレイ期間DELA Y8#が経過している（ステップ１３４、１３５）、
ときに、ステップ１３６で燃料性状の推定を許可し（推定許可フラグ＝１）、そうでなければステップ１３７に移行して燃料性状の推定を禁止する（推定許可フラグ＝０）。
【０１８２】
なお、上記のＡ）〜Ｈ）の各条件は様々な仕様のエンジンや車両があることを考慮して単に羅列したものである。したがって、エンジンや車両の機種によっては不要なものがあるので、そのときにはその不要な条件を削ればよい。たとえば、車両がマニュアル仕様のときは、上記のＧ）は不要である。簡単にはいずれか一つの条件だけで構成することもできる。
【０１８３】
ここで、ａ）パージ中、ｂ）ブレーキスイッチのＯＮ時、ｃ）気筒分配不安定域、ｄ）失火判定時、ｅ）ＥＧＲ中、ｆ）スワールコントロールバルブの切換直後、ｇ）非ロックアップ中、ｈ）燃料カット中の各場合に燃料性状の推定を禁止するのは、これらの場合に燃料性状以外の要因で排気空燃比が変動するため、これらの場合にまで排気空燃比を出力データとしてサンプリングしたのでは、データが不正確となり、この不正確なデータに基づいて燃料性状を推定すると推定精度が低下するからである。
【０１８４】
以下、上記ａ）〜ｇ）の各場合毎に排気空燃比への影響を詳述する。
【０１８５】
ａ）燃料タンク内で蒸発する燃料蒸気をキャニスターに導いてキャニスター内の活性炭に吸着させておき、所定の運転条件（パージＯＮの条件）になると、パージ弁を開き、絞り弁下流に発達する吸入負圧と、キャニスターに設けられる大気導入路からの新気を利用して、活性炭に吸着している燃料蒸気を離脱させて吸気管内に導入するようにした、いわゆる蒸発燃料処理装置を備えるエンジンがある。、このエンジンでは、運転前にかなりの期間放置されていると、運転に入って最初のパージ中（パージ弁の開時）にはパージ禁止中（パージ弁の全閉時）よりも排気空燃比がリッチになる。
【０１８６】
ｂ）制動能力を補助するためブレーキペダルを踏み込んでいない状態では、パワーシリンダ内でパワーピストンによって区画された両室に絞り弁下流に発達する負圧を導入しておき、ブレーキペダルを踏み込んだとき、バルブの切換によりパワーシリンダ内の一方の室にのみ大気を切換導入して２つの室に圧力差（負圧と大気圧の差）を生じさせ、この圧力差によりパワーピストンを作動させてパワーピストンのプッシュロッド先端についているハイドロリックピストンを動かすことにより、マスターシリンダからきた油圧を増大させて各ホイールシリンダに送り込むようにした、いわゆるハイドロバックがある。また、倍力の原理はハイドロバックと全く同じでマスターシリンダの手前においてマスターシリンダのピストンを押す力を倍力するマスターバックがある。これらは、絞り弁下流に発達する負圧を利用するブレーキ倍力装置である。このブレーキ倍力装置を備える車両では、ブレーキペダルを踏み込んだ場合に、ブレーキ倍力装置の作動により吸入負圧が変動するので、その影響を受けて壁流燃料量が変化し、排気空燃比がブレーキ倍力装置の非作動時よりリーンになる。この場合に、ブレーキ倍力装置が作動したかどうかは、ブレーキスイッチをみればわかる。つまり、ブレーキスイッチのＯＮ時をブレーキ倍力装置の作動時であると、またブレーキスイッチのＯＦＦ時をブレーキ倍力装置の非作動時であるとみなせばよい。
【０１８７】
ｃ）気筒分配不安定域（気筒分配の影響を受けて空燃比が不安定になる領域）をエンジンの負荷と回転数をパラメータとして予め定めているエンジンがある。このエンジンでは気筒分配不安定域になると、気筒分配安定域よりも排気空燃比がリーンになったりリッチになったりする。ここで、「気筒分配」とは、気筒間の燃料分配を縮めていったものである。
【０１８８】
ｄ）診断に活かすため失火判定を行っているエンジンでは、失火判定時に非失火時より排気空燃比がリーンになったりリッチになったりする（失火にはリッチ失火とリーン失火があるので）。
【０１８９】
ｅ）ＮＯｘの排出低減のためＥＧＲを行うエンジンがある。ＥＧＲガスには未燃分と不活性ガスとを含むので、ＥＧＲ中は排気空燃比が不安定となり、ＥＧＲ禁止中よりも空燃比がリーンになったりリッチになったりする。
【０１９０】
ｆ）低負荷時の燃焼を改善するため吸気ポートにスワールコントロールバルブを備えるエンジンがある。このエンジンでは、スワールコントロールバルブが閉状態になると壁流燃料量が変化する（吸気流速が大きくなり壁流燃料量が減小する）ため、排気空燃比に影響する。
【０１９１】
ｇ）トルクコンバータの入力軸と出力軸を直結状態とする、いわゆるロックアップ機構付きの自動変速機を備える車両がある。この車両では、ロックアップ時より非ロックアップ時のほうがエンジン回転の吹き上がりが早く、逆に回転の落ちも早い。つまり、非ロックアップ時には排気空燃比が不安定になりやすく、これによってロックアップ時よりも排気空燃比がリーンになったりリッチになったりする。
【０１９２】
ｈ）省燃費のため減速時などに燃料供給を停止する、いわゆる燃料カットを行うエンジンがある。このエンジンでは、燃料カット中や燃料カットからのリカバー直後は壁流燃料量が変化するので、排気空燃比に影響する。
【０１９３】
次に、ステップ１２２、１２４、１２６、１２８、１３０、１３１、１３３、１３５でディレイ期間（たとえば時間）が経過していることをも条件としているのは、パージを禁止した直後、ブレーキスイッチがＯＦＦになった直後、気筒分配安定域に移った直後、失火判定の解除直後、ＥＧＲを禁止した直後、スワールコントロールバルブを切換えた直後、ロックアップした直後、燃料カットリカバー直後よりしばらくの間、いずれも排気空燃比が安定しないので、この期間も燃料性状の推定を禁止するようにしたものである。なお、各ディレイ期間は、マッチングにより最適値を定めればよい。
【０１９４】
なお、パージ禁止中であるかどうかはパージ弁への出力信号により、ＥＧＲ禁止中であるかどうかはＥＧＲ弁への出力信号により、スワールコントロールバルブの作動状態はスワールコントロールバルブへの出力信号により、ロックアップ中かどうかはロックアップクラッチを断接するためのソレノイドへの出力信号により、気筒分配安定域であるかどうかはエンジンの負荷と回転数により定まる運転点が気筒分配不安定域にあるかどうかにより、失火判定されているかどうかは失火判定のフローより、燃料カット中かどうかや燃料カットリカバーされたかどうかは燃料噴射制御のフローより知ることができる。
【０１９５】
このように、燃料性状以外の要因で排気空燃比が変動する場合にも、排気空燃比を出力データとしてサンプリングしたのでは不正確なデータとなり、この不正確なデータに基づいて燃料性状を推定すると、推定精度が低下するのであるが、本実施形態では、このような場合にデータサンプリング（したがって燃料性状の推定）を禁止することで、推定精度の低下を防止できる。
【０１９６】
さて、このようにして燃料性状の推定許可の判定が終了したら、図１４に戻り、ステップ８で推定許可判定フラグをみる。推定許可判定フラグ＝０（推定禁止条件）のときはステップ９、１０に移行し、排気空燃比の読み込み数（サンプリング数）ｓ１に０を入れるとともに、全ての排気空燃比データ（図示しないが、入力データである実噴射パルス幅のデータも）を消去する。
【０１９７】
ステップ９、１０でサンプリング数を０に初期化するとともに全ての排気空燃比データを消去するようにしたのは次の理由からである。排気空燃比の応答波形の解析（ステップ１２で後述する）のためには、過渡の初期から終期にわたる一連のデータが必要になるところ、過渡の途中で燃料性状以外の要因で排気空燃比が変動する場合にも、排気空燃比を出力データとしてサンプリングしたのでは、不正確なデータが混じって排気空燃比の応答波形の解析を精度良く行うことができなくなるので、このときには１からサンプリングをやり直すためである。
【０１９８】
一方、推定許可判定フラグ＝１（推定許可条件）のときはステップ８よりステップ１１、１２に進み、上記のＮ個ずつの入出力データを用いて実噴射パルス幅がステップ変化したときの排気空燃比の応答波形を解析し、その解析結果から使用燃料の燃料性状を推定する。
【０１９９】
ここで、「排気空燃比の応答波形の解析」とは、前述の表現によれば、入出力データに基づいてＡＲＸモデル（プラントモデル）のパラメータθを規範モデルとの予測誤差が最小となるように調整してＡＲＸモデルを同定することである。そこでＡＲＸモデルの同定を図１５のサブルーチンにより、また燃料性状の推定について図１６のサブルーチンにより説明する。
【０２００】
まず図１５において、ステップ２１では、バッファにある入出力データ（入力についてｕ(１)〜ｕ(128)、出力について−ｙ(１)〜−ｙ(128)）より数３２式を用いてデータベクトルψ(ｋ)を作成する。
【０２０１】
ステップ２２ではこのデータベクトルψ(ｋ)から上記の数３３式を用いてＲ(Ｎ)を、またステップ２３では出力データｙ(ｋ)とこのデータベクトルψ(ｋ)から上記の数３４式を用いてｆ(Ｎ)を演算し、これらＲ(Ｎ)、ｆ(Ｎ)からステップ２４において上記の数２８式を用いてモデルパラメータθを演算する。
【０２０２】
次に、図１６に移り、このようにして求めたモデルパラメータθからステップ３１において離散時間系ＬＴＩシステムの伝達関数Ｇ(ｑ，θ)を演算する（θから上記の数２９式、数３０式を用いてＡ(ｑ)、Ｂ(ｑ)を作成し、この２つよりＧ(ｑ，θ)（＝Ｂ(ｑ)／Ａ(ｑ)）を算出する）。
【０２０３】
このシステム伝達関数Ｇ(ｑ，θ)からステップ３２においてＡＲＸモデルのカットオフ周波数ｆｃ_Realを演算する。ステップ３３ではこのカットオフ周波数ｆｃ_Realと規範モデルのカットオフ周波数ｆｃ_Refを比較する。
【０２０４】
ここで、基準燃料に重質ガソリンを用いているので、軽質ガソリンが使用されていればｆｃ_Real＞ｆｃ_Refとなり、重質ガソリンが使用されているときはｆｃ_Real≦ｆｃ_Refとなる。したがって、ｆｃ_Real＞ｆｃ_Refのとき（軽質ガソリンの使用時）はステップ３４に進んで燃料性状切換フラグ＝１とし、これに対して、ｆｃ_Real≦ｆｃ_Refのとき（重質ガソリンの使用時）は、ステップ３３よりステップ３５に進んで燃料性状切換フラグ＝０とする。
【０２０５】
このようにしていずれの燃料が使用されているのかの判定が終了したら、図１４のステップ１３に進み、燃料性状切換フラグの値（燃料性状の判定結果）をＥＥＰＲＯＭに格納したあと、ステップ１４において燃料性状判定済みフラグ＝１とする。この燃料性状判定済みフラグ＝１の処理により、次回以降は、図１４のステップ２以降に進むことができない（燃料性状の判定回数が１回だけとなる）。
【０２０６】
このようにして燃料性状の判定が可能になると、燃料噴射量の各種の補正量や始動時燃料噴射量を燃料性状の違いに応じて与えることができる。これを具体的にＫＡＳの場合で説明する。
【０２０７】
図１７は、始動後増量補正係数ＫＡＳを演算するためのもので、一定時間毎（たとえば１０ｍｓ毎）に実行する。
【０２０８】
ステップ４１でＥＥＰＲＯＭに格納されている燃料性状切換フラグを読み込む。ステップ４２ではスタータスイッチをみてこれがＯＮのときは、ステップ４３に進み、冷却水温ＴＷと回転数Ｎｅを読み込む。このうち冷却水温ＴＷと燃料性状切換フラグの値から、ステップ４４、４５においてそれぞれ図１８、図１９を内容とするテーブルを検索することにより始動後増量水温補正値ＴＫＡＳ、第２始動後増量補正係数ＫＡＳＳを、また回転数Ｎｅと燃料性状切換フラグの値からステップ４６において図２０を内容とするテーブルを検索することにより始動後増量回転補正値ＴＮＫＡＳを演算し、これらの値を用いステップ４７において
【０２０９】
【数３６】
ＫＡＳ＝ＴＫＡＳ×ＴＮＫＡＳ＋ＫＡＳＳ
の式により始動後増量補正係数ＫＡＳを算出する。
【０２１０】
ステップ４８では、スタータスイッチがＯＦＦになってからの処理に備えるため、ＴＫＡＳの値をＴＫＡＳ_n-1に、ＫＡＳＳの値をＫＡＳＳ_n-1に移して今回の処理を終了する。ＴＫＡＳ_n-1、ＫＡＳＳ_n-1は前回値を保持するためのメモリである。
【０２１１】
やがてスタータスイッチがＯＦＦになると（始動完爆）、ステップ４２よりステップ４９以降の減衰操作に進む。
【０２１２】
ステップ４９では、燃料性状切換フラグの値と始動後時間ｔとから図２１を内容とするテーブルを検索することにより始動後増量減少時間割合ＴＭＫＡＳを演算し、ステップ５０でこの値だけ前回値を減少させた値を今回のＴＫＡＳ（＝ＴＫＡＳ_n-1−ＴＭＫＡＳ）として算出する。スタータスイッチがＯＦＦになった直後はＴＫＡＳ＞０であるので、そのままステップ５３に進む。
【０２１３】
ステップ５３〜５６はステップ４９〜５２と同様である。ステップ５３で燃料性状判定フラグの値と始動後時間ｔから図２２を内容とするテーブルを検索することにより第２始動後増量減少時間割合ＴＭＫＡＳＳを演算し、ステップ５４でこの値だけ前回値を減少させた値を今回のＫＡＳＳ（＝ＫＡＳＳ_n-1−ＴＭＫＡＳＳ）として算出する。このときも、ＫＡＳＳ＞０であるので、そのままステップ４６に進んでステップ３６以降の処理を実行する。
【０２１４】
次回以降はステップ４９、５０、５３、５４を繰り返すことになるので、やがてＴＫＡＳやＫＡＳＳが０以下となり、このときはステップ５２やステップ５６に進んでＴＫＡＳやＫＡＳＳを０に制限する。
【０２１５】
この結果、ＴＫＡＳ、ＫＡＳＳとも、スタータスイッチのＯＦＦ時の値を初期値として、スタータスイッチのＯＦＦ後に一定の割合で減衰して０になる（ただし、ＴＮＫＡＳが一定のとき）。ただし、ＴＫＡＳの初期値のほうがＫＡＳＳの初期値より大きく、かつＴＫＡＳの減少時間割合のほうがＫＡＳＳの減少時間割合より大きい。したがって、ＴＫＡＳとＫＡＳＳを加算した値であるＫＡＳは、スタータスイッチＯＦＦ時のＴＫＡＳの値とＫＡＳＳの値の合計を初期値として、スタータスイッチＯＦＦ後にまず急激な勾配で小さくなり、ＴＫＡＳが０になったタイミングからは緩やかな勾配に切換わって減少していく。
【０２１６】
この場合に、軽質ガソリンの使用時のほうが重質ガソリンの使用時よりもＴＫＡＳ、ＫＡＳＳの各初期値（図１８、図１９のテーブル値）を小さく、かつＴＫＡＳ、ＫＡＳＳの各減少時間割合（図２１、図２２のテーブル値）を大きくしているので、軽質ガソリン使用時のＫＡＳは、重質ガソリン使用時のＫＡＳより小さくなる（図２３参照）。つまり、燃料性状の判定を行っていないものでは、軽質ガソリンの使用時にも、重質ガソリンに対してマッチングしたテーブル値を用いることによる空燃比のリッチ化を招くのであるが、このように、軽質ガソリンの使用であることを判定したときは、次回の始動時のＫＡＳの演算に際して、軽質ガソリン用のＫＡＳを演算することで、軽質ガソリンの使用時にも空燃比がリッチ側に偏ることがなくなるのである。
【０２１７】
図２４のフローチャートは第２実施形態で、第１実施形態の図１６に対応する。図１６と同一部分には同一のステップ番号を付している。
【０２１８】
基準燃料に重質ガソリンを用いた第１実施形態に対して、第２実施形態は、市販されている燃料のうち揮発性が悪くもなく良くもないほぼ中間の燃料を基準燃料として、またこの基準燃料よりも揮発性の良い燃料を軽質ガソリン、この逆に基準燃料よりも揮発性の悪い燃料を重質ガソリンとして設定しておき、プラントモデルのカットオフ周波数と規範モデルのカットオフ周波数（つまり基準燃料に対するカットオフ周波数）の差を演算し、この周波数差と許容範囲とを比較して使用されている燃料の燃料性状を判定するようにしたもので、これによって、基準燃料に対するカットオフ周波数がバラツクことがあっても、燃料性状の推定を安定して行うことができる。
【０２１９】
図２４において、図１６と相違する部分を主に述べると、ステップ６１で
【０２２０】
【数３７】
Δｆｃ＝ｆｃ_Real−ｆｃ_Ref
の式により基準燃料とのカットオフ周波数差Δｆｃを計算し、この周波数差Δｆｃの絶対値と許容範囲を定める所定値ａ（＞０）、あるいはΔｆｃとａをステップ６２、６３において比較する。｜Δｆｃ｜≦ａ（つまり基準燃料が使用されている）であれば、ステップ６２よりステップ６４に進んで燃料性状切換２フラグ＝０とし、｜Δｆｃ｜＞ａかつΔｆｃ＞ａ（つまり軽質ガソリンが使用されている）であるときはステップ６３よりステップ６５に進んで燃料性状切換２フラグ＝１とし、それ以外（つまり重質ガソリンが使用されている）のときはステップ６３よりステップ６６に進んで燃料性状切換２フラグ＝２とする。
【０２２１】
このように第２実施形態では、使用されている燃料が、基準燃料、軽質ガソリン、重質ガソリンのいずれであるかが判定された。
【０２２２】
ただし、第２実施形態のように、燃料性状判定値が３つの値になると、始動後増量補正係数ＫＡＳを演算するに際し、図１８〜図２２に対応して３種類のテーブル値を用意する必要がある。
【０２２３】
次に、図２５、図２６、図２８のフローチャートは第３実施形態で、それぞれ第１実施形態の図１４、図１６、図１７に対応する。図２５において図１４と同一部分に、図２６において図１６と同一部分に、また図２８において図１７と同一部分にそれぞれ同一のステップ番号を付している。
【０２２４】
前述の２つの実施形態が燃料性状判定値（つまり燃料性状切換フラグや燃料性状切換２フラグの値）が２値あるいは３値であったのに対して、第３実施形態は、連続値としての燃料性状推定値を演算し、これをＥＥＰＲＯＭに格納するとともに（図２５のステップ７１、７２）、次回の始動時よりこの燃料性状推定値を用いて始動後増量補正係数ＫＡＳを演算するようにしたものである。
【０２２５】
燃料性状推定値の演算について具体的に図２６により説明すると、ステッ３１、３２で第１実施形態と同じにプラントモデルのカットオフ周波数を演算し、その演算したカットオフ周波数からステップ８１において図２７を内容とするテーブルを検索することにより燃料性状推定値を演算する。プラントモデルのカットオフ周波数と燃料性状推定値との関係は図２７のようになるので、同特性を予めマッチングにより定めておけば、プラントモデルのカットオフ周波数から使用燃料の燃料性状を推定できるのである。
【０２２６】
次に、図２８において、図１７と異なる部分を主に説明すると、ステップ９１で燃料性状推定値ＦＣを読み込み、スタータスイッチのＯＮ時はこの値ＦＣと冷却水温ＴＷ、回転数Ｎeからステップ９２、９３、９４において図２９、図３０、図３１を内容とするマップを検索することにより、始動後増量水温補正値ＴＫＡＳ、第２始動後増量補正係数ＫＡＳＳ、始動後増量回転補正値ＴＮＫＡＳを、またスタータスイッチのＯＦＦ時には燃料性状推定値ＦＣと冷却水温ＴＷからステップ９５、９６において図３２、図３３を内容とするマップを検索することにより、始動後増量減少時間割合ＴＭＫＡＳ、第２始動後増量減少時間割合ＴＭＫＡＳＳをそれぞれ演算する。
【０２２７】
ここで、ＴＫＡＳ、ＫＡＳＳは、図２９、図３０に示したように同一のＦＣであれば冷却水温ＴＷが低いほど、またＴＷが同じであるとき燃料性状が重質になるほど大きくなる値、ＴＭＫＡＳ、ＴＭＫＡＳＳは、図３２、図３３のように同一のＦＣであれば冷却水温ＴＷが高くなるほど、またＴＷが同じであるとき燃料性状が軽質になるほど大きくなる値である。
【０２２８】
なお、燃料性状推定値とＴＷが同一であれば、ＴＫＡＳのほうがＫＡＳＳより大きく、かつＴＭＫＡＳのほうがＴＭＫＡＳＳより大きくなることはいうまでもない。
【０２２９】
この第３実施形態によれば、連続値としての燃料性状推定値ＦＣに応じて始動後増量補正係数ＫＡＳの演算に用いるデータ（マップ値）を割り付けているので、先の２つの実施形態よりも、始動後増量補正係数ＫＡＳの演算精度が向上する。
【０２３０】
図３４のフローチャートは第４実施形態で、第３実施形態の図２８と置き換わるものである。なお、図２８と同一部分には同一のステップ番号を付している。
【０２３１】
さて、ＫＡＳを演算するのに用いるデータを、図２９〜図３３のようにマップ値で与えるのでは、マッチングの工数が莫大なものとなってしまう。そこでこの第４実施形態は、燃料性状推定値ＦＣに応じた燃料性状補正値ＫＦＣを導入してこの補正値ＫＦＣで最重質ガソリンに対してマッチングしたデータ（テーブル値）を補正し、この補正したデータに基づいて始動後増量補正係数ＫＡＳを演算することにより、マッチングの工数を減らすようにしたものである。
【０２３２】
具体的に説明すると、図２８の場合と異なるのは、ステップ１０１、１０２〜１１５である。まずステップ１０１で燃料性状推定値ＦＣから図３５を内容とするテーブルを検索することにより、燃料性状補正値ＫＦＣを演算する。図３５に示したように、ＫＦＣは、最重質ガソリン（燃料性状が最重質）のときを最大の１．０として燃料性状が軽質になるほど小さくなる値である。
【０２３３】
ステップ１０２、１０３では冷却水温ＴＷから図３６、図３７を内容とするテーブルを検索することにより、ＴＫＡＳ、ＴＭＫＡＳ（いずれも最重質ガソリンに対してマッチングした値である）を演算し、これらと上記のＫＦＣとを用いステップ１０４において、
【０２３４】
【数３８】
ＴＫＡＳＦ＝ＴＫＡＳ×ＫＦＣ
ＴＭＫＡＳＦ＝ＴＭＫＡＳ×ＫＦＣ
の式により、燃料性状対応の始動後増量水温補正値ＴＫＡＳＦと燃料性状対応の始動後増量減少時間割合ＴＭＫＡＳＦを計算する。ステップ１０５、１０６、１０７ではステップ１０２、１０３、１０４と同様にして、冷却水温ＴＷから図３８、図３９を内容とするテーブルを検索することにより、ＫＡＳＳ、ＴＭＫＡＳＳ（これらも最重質ガソリンに対してマッチングした値である）を演算し、
【０２３５】
【数３９】
ＫＡＳＳＦ＝ＫＡＳＳ×ＫＦＣ
ＴＭＫＡＳＳＦ＝ＴＭＫＡＳＳ×ＫＦＣ
の式により、燃料性状対応の第２始動後増量補正係数ＫＡＳＳＦと燃料性状対応の第２始動後増量減少時間割合ＴＭＫＡＳＳＦを計算する。そして、これらの値を用いて、上記の数３６式と同様の式である、
【０２３６】
【数４０】
ＫＡＳ＝ＴＫＡＳＦ×ＴＮＫＡＳ＋ＫＡＳＳＦ
の式により始動後増量補正係数ＫＡＳを算出する（ステップ１０８）。
【０２３７】
そしてステップ１０９ではスタータスイッチがＯＦＦになってからの処理に備えるため、ＴＫＡＳＦの値をＴＫＡＳＦ_n-1に、ＫＡＳＳＦの値をＫＡＳＳＦ_n-1に移して今回の処理を終了する。ステップ１１０〜１１５は、スタータスイッチのＯＦＦ後にＴＫＡＳＦ、ＫＡＳＳＦについて図１７のステップ４９〜５６と同様に減衰操作を行う部分である。
【０２３８】
たとえば、最重質ガソリンよりも燃料性状が軽質側のガソリンが使用されるときには、ＫＦＣが１．０より小さな値となるため、ＴＫＡＳＦ＜ＴＫＡＳ、ＴＭＫＡＳＦ＜ＴＭＫＡＳ、ＫＡＳＳＦ＜ＫＡＳＳ、ＴＭＫＡＳＳＦ＜ＴＭＫＡＳＳとなることから、最重質ガソリンに対するＫＡＳよりも小さなＫＡＳが算出され、これによって、図２８の場合と同様に、最重質ガソリンよりも燃料性状が軽質側のガソリンに対しても最適な始動後増量補正係数が与えられるのである。なお、最重質ガソリンの使用時は、ＫＦＣ＝１．０より、ＴＫＡＳＦ＝ＴＫＡＳ、ＴＭＫＡＳＦ＝ＴＭＫＡＳ、ＫＡＳＳＦ＝ＫＡＳＳ、ＴＭＫＡＳＳＦ＝ＴＭＫＡＳＳとなり、従来装置と変わらない。
【０２３９】
この場合に、ＫＡＳの演算に用いるデータを得るに際しては、図３６〜図３９に示す特性を最重質ガソリンに対してマッチングするだけで済むので、第４実施形態によれば、第３実施形態の場合よりマッチングの工数を低減できるのである。
【０２４０】
前述の第１、第３、第４の各実施形態では噴射量補正量としての始動後増量補正係数ＫＡＳを対象として、（Ａ）燃料性状切換フラグを用いる場合、（Ｂ）燃料性状推定値ＦＣを用いる場合、（Ｃ）燃料性状補正値ＫＦＣを用いる場合で説明したが、これに限られるものでない。たとえば、次の（１）〜（４）の噴射量補正量や（５）、（６）の燃料噴射量を対象として、上記（Ａ）〜（Ｃ）の３つの場合とも適用できる。
【０２４１】
（１）低周波成分（壁流燃料）。
【０２４２】
（２）高周波成分（壁流燃料）。
【０２４３】
（３）水温増量補正量。
【０２４４】
（４）未燃分増量補正量。
【０２４５】
（５）始動時燃料噴射量。
【０２４６】
（６）加速時割り込み噴射量。
【０２４７】
ここで、（１）、（２）については特願平８−１７３８０２号により、（３）、（４）については特願平８−１７３８０３号により、（５）については特開昭７−６３０８２号公報により、（６）については特開昭６４−３２４５号公報により公知であるので、詳細は説明しない。
【０２４８】
実施形態では、過渡時に燃料噴射量に対する排気空燃比の応答波形をサンプリングし、これら過渡時データに基づいて、予めＥＣＭ上に構築したプラントモデルのパラメータを、基準燃料に対するプラントモデルである規範モデルとの予測誤差が最小となるように調整することにより、使用燃料に対するプラントモデルを同定する場合で説明したが、これに限られるものでなく、燃料噴射量に代えて燃料供給量を用いることもできる。また、予測誤差が最小となるように調整するほか、予測誤差が小さくなるように調整することでもかまわない。
【０２４９】
また、使用燃料の燃料性状の推定方法は、実施形態のものに限られない。
【図面の簡単な説明】
【図１】エンジン制御の制御システム図。
【図２】燃料性状の推定に関係する制御システム図。
【図３】エンジンプラントモデルのブロック図。
【図４】燃料挙動のモデル図。
【図５】燃料挙動のパラレルパスブロック図。
【図６】排気モデル図。
【図７】入出力間の無駄時間を表す波形図。
【図８】無駄時間を分類した表図。
【図９】ＬＴＩシステムの一般的なブロック図。
【図１０】評価関数（評価規範）の特性図。
【図１１】ＡＲＸモデルの同定手法を示すフローチャート。
【図１２】モデル同定に必要な入力信号とその応答を示す波形図。
【図１３】同定結果と実データを重ねて示すボード線図。
【図１４】燃料性状の推定を説明するためのフローチャート。
【図１５】ＡＲＸモデルの同定を説明するためのフローチャート。
【図１６】燃料性状の切換判定を説明するためのフローチャート。
【図１７】始動後増量補正係数ＫＡＳの演算を説明するためのフローチャート。
【図１８】始動後増量水温補正値（初期値）の特性図。
【図１９】第２始動後増量補正係数（初期値）の特性図。
【図２０】始動後増量回転補正値の特性図。
【図２１】始動後増量減少時間割合の特性図。
【図２２】第２始動後増量減少時間割合の特性図。
【図２３】始動後増量補正係数ＫＡＳの時系列イメージを示す波形図。
【図２４】第２実施形態の燃料性状の切換判定を説明するためのフローチャート。
【図２５】第３実施形態の燃料性状の推定を説明するためのフローチャート。
【図２６】第３実施形態の燃料性状推定値の演算を説明するためのフローチャート。
【図２７】カットオフ周波数に対する燃料性状推定値の特性図。
【図２８】第３実施形態の始動後増量補正係数ＫＡＳの演算を説明するためのフローチャート。
【図２９】第３実施形態の始動後増量水温補正値（初期値）の特性図。
【図３０】第３実施形態の第２始動後増量補正係数（初期値）の特性図。
【図３１】第３実施形態の始動後増量回転補正値の特性図。
【図３２】第３実施形態の始動後増量減少時間割合の特性図。
【図３３】第３実施形態の第２始動後増量減少時間割合の特性図。
【図３４】第３実施形態の始動後増量補正係数ＫＡＳの演算を説明するためのフローチャート。
【図３５】第３実施形態の燃料性状補正値の特性図。
【図３６】第３実施形態の始動後増量水温補正値（初期値）の特性図。
【図３７】第３実施形態の始動後増量減少時間割合の特性図。
【図３８】第３実施形態の第２始動後増量補正係数（初期値）の特性図。
【図３９】第３実施形態の第２始動後増量減少時間割合の特性図。
【図４０】燃料性状の推定許可判定を説明するためのフローチャート。
【図４１】燃料性状の推定許可判定を説明するためのフローチャート。
【図４２】第１の発明のクレーム対応図。
【図４３】第２の発明のクレーム対応図。
【図４４】第３の発明のクレーム対応図。
【図４５】第９の発明のクレーム対応図。
【図４６】第１０の発明のクレーム対応図。
【図４７】第１１の発明のクレーム対応図。
【符号の説明】
２ ＥＣＭ
３ Ａ／Ｆセンサ
７ 燃料噴射弁
１４ ＥＥＰＲＯＭ
２１ プラント同定部
２２ 燃料性状推定部
２３ トリガリング機能
２４ コントローラ
３１ プラントモデル
３７ 規範モデル
３８ 比較手段[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for detecting fuel properties and an engine fuel supply control apparatus using the detection result.
[0002]
[Prior art]
During cold start when the engine becomes unstable, the fuel is increased by an increase correction coefficient after starting, and the engine is stabilized by setting the air-fuel ratio to a value on the rich side of the stoichiometric air-fuel ratio. (See Kaihei 6-105129)
[0003]
[Problems to be solved by the invention]
By the way, the reason why the injection amount correction is necessary is as follows. More specifically, the fuel injection valve provided in front of the intake port, the injected fuel from the injection valve is not entirely injected into the cylinder while being sprayed, It adheres to the part and intake port wall and becomes liquid. The fuel adhering to the intake port wall reaches the cylinder while slowly passing through the port wall while being in a liquid state. That is, only this amount of fuel (wall flow fuel) causes a delay in fuel supply.
[0004]
In this case, the amount of wall flow fuel further depends on the property (particularly volatility) of the fuel, and the wall flow fuel amount increases as the fuel has lower volatility. Considering the fuel wall flow difference due to the difference in the volatility of these fuels, with the various injection amount corrections in the past, even when the most volatile fuel (the heaviest gasoline) is used, Matched so that the engine rotation during cold does not become unstable. If it is the post-startup increase correction coefficient, the data used when calculating the post-startup increase correction coefficient is matched with the heaviest gasoline.
[0005]
However, when fuel with better volatility than the heaviest gasoline is used, various injection amount correction amounts become too large, which causes the air-fuel ratio to lean toward the richer side than when using the heaviest gasoline. Emissions (especially CO and HC) are worsened.
[0006]
Therefore, it is conceivable to sample the response waveform of the exhaust air / fuel ratio with respect to the fuel injection amount at the time of transition, and to estimate the fuel property of the fuel used based on the data at the time of transition. For example, by adjusting the parameters of the plant model that has been built in advance on the ECM (Electronic Control Module) based on the above transient data so that the prediction error with the reference model that is the plant model for the reference fuel is minimized. The plant model for the used fuel is identified, and the cut-off frequency of the identified plant model is compared with the cut-off frequency for the reference model to enable estimation of the fuel properties of the used fuel. It has been proposed almost simultaneously with the application (see Japanese Patent Application No. 11-98709).
[0007]
In this case, the exhaust air-fuel ratio varies greatly even with factors (disturbances) other than fuel properties. For example, factors other than fuel properties include fluctuations in suction negative pressure accompanying the operation of brake boosters such as purge gas, hydromaster and masterback, cylinder distribution, misfire, EGR, swirl control valve operating status, lockup, fuel There are cut and blow-by gas. For this reason, even when the exhaust air-fuel ratio changes due to factors other than the fuel property even during the transition, if the input / output data is sampled, the data becomes inaccurate, and the accuracy of estimation of the fuel property falls.
[0008]
Therefore, the present invention determines whether or not the exhaust air-fuel ratio fluctuates due to factors other than fuel properties, and prohibits sampling of input / output data when the exhaust air-fuel ratio fluctuates due to factors other than fuel properties. Accordingly, an object of the present invention is to prevent the sampling data from becoming inaccurate and to avoid a decrease in the estimation accuracy of the fuel property.
[0010]
[Means for Solving the Problems]
  First1The invention42As shown, the means 51 for calculating the fuel supply amount according to the operating condition of the engine, the means 52 for supplying the supply amount of fuel to the engine, the means 53 for detecting the exhaust air-fuel ratio of the engine, The fuel supply amount is input, and the exhaust air / fuel ratio is output, and the means 54 for sampling the response waveform data of the exhaust air / fuel ratio with respect to the fuel supply amount with the currently used fuel and the input / output data are preliminarily constructed. By adjusting the parameters of the plant model so as to reduce the prediction error with respect to the reference model, means 61 for identifying the plant model for the fuel used, and the cut-off frequency fc of the identified plant model_RealAnd a cut-off frequency fc of this plant model_RealAnd the cut-off frequency fc of the reference model_RefAnd means 63 for estimating the fuel property of the fuel used, and a region where the exhaust air-fuel ratio fluctuates due to a factor other than the fuel propertyIs one of the following states 1 to 15And a region in which the exhaust air-fuel ratio fluctuates due to a factor other than the fuel property based on the determination result.Is one of the following states 1 to 15And means 57 for prohibiting the sampling of the input / output data.
State 1: The fuel vapor that evaporates in the fuel tank is guided to the canister and adsorbed on the activated carbon in the canister, the purge valve is opened under the purge ON condition, the suction negative pressure developed downstream of the throttle valve, and the canister In the case where a device is provided that uses fresh air from the air introduction path to separate the fuel vapor adsorbed on the activated carbon and introduces it into the intake pipe, the purge is being performed (when the purge valve is open).
State 2: The fuel vapor that evaporates in the fuel tank is guided to the canister and adsorbed to the activated carbon in the canister, the purge valve is opened when the predetermined operating condition is reached, the suction negative pressure developed downstream of the throttle valve, and the canister Purging is prohibited (when the purge valve is fully closed) and purged when equipped with a device that uses fresh air from the installed air introduction path to release the fuel vapor adsorbed on the activated carbon and introduce it into the intake pipe. This is a state in which the delay period has not passed since the prohibition.
State 3: When a brake booster using a negative pressure developed downstream of the throttle valve is provided, the brake switch is ON.
State 4: When a brake booster that uses negative pressure developed downstream of the throttle valve is provided, the delay period has not elapsed since the brake switch is turned off and the brake switch is turned off.
State 5: This cylinder distribution instability region is a cylinder distribution instability region when the engine load and the rotational speed are set in advance as parameters.
State 6: When the cylinder distribution unstable region is predetermined with the engine load and the engine speed as parameters, the cylinder distribution stable region is in the cylinder distribution stable region and the delay period has not elapsed. is there.
State 7: When a misfire determination function is provided, it is a misfire determination time.
State 8: When the misfire determination function is provided, the delay period has not elapsed since the misfire determination is canceled and the misfire determination is canceled.
State 9: EGR is being performed when an EGR device is provided.
State 10: In the case where an EGR device is provided, the delay period has not elapsed since EGR is prohibited and EGR is prohibited.
State 11: When a swirl control valve is provided, the delay period has not elapsed since the swirl control valve is closed or opened.
State 12: When an automatic transmission with a lockup mechanism is provided, the lockup is not in progress.
State 13: In the case where an automatic transmission with a lock-up mechanism is provided, the delay period has not elapsed since the lock-up and the lock-up.
State 14: When a fuel cut function is provided, the fuel is being cut.
State 15: In a case where the fuel cut function is provided, the fuel is not being cut and the delay period has not elapsed since the fuel cut is recovered.
[0011]
  First2The invention43As shown, the means 51 for calculating the fuel supply amount according to the operating condition of the engine, the means 52 for supplying the supply amount of fuel to the engine, the means 53 for detecting the exhaust air-fuel ratio of the engine, The fuel supply amount is input, and the exhaust air / fuel ratio is output, and the means 54 for sampling the response waveform data of the exhaust air / fuel ratio with respect to the fuel supply amount with the currently used fuel and the input / output data are preliminarily constructed. By adjusting the parameters of the plant model so as to reduce the prediction error with respect to the reference model, means 61 for identifying the plant model for the fuel used, and the cut-off frequency fc of the identified plant model_RealAnd a cut-off frequency fc of this plant model_RealAnd the cut-off frequency fc of the reference model_RefMeans for estimating the fuel property of the fuel used by comparing the difference between the difference and the allowable range, and the region where the exhaust air-fuel ratio fluctuates due to a factor other than the fuel propertyIs one of the following states 1 to 15And a region in which the exhaust air-fuel ratio fluctuates due to a factor other than the fuel property based on the determination result.Is one of the following states 1 to 15And means 57 for prohibiting the sampling of the input / output data.
State 1: The fuel vapor that evaporates in the fuel tank is guided to the canister and adsorbed on the activated carbon in the canister, the purge valve is opened under the purge ON condition, the suction negative pressure developed downstream of the throttle valve, and the canister In the case where a device is provided that uses fresh air from the air introduction path to separate the fuel vapor adsorbed on the activated carbon and introduces it into the intake pipe, the purge is being performed (when the purge valve is open).
State 2: The fuel vapor that evaporates in the fuel tank is guided to the canister and adsorbed to the activated carbon in the canister, the purge valve is opened when the predetermined operating condition is reached, the suction negative pressure developed downstream of the throttle valve, and the canister Purging is prohibited (when the purge valve is fully closed) and purged when equipped with a device that uses fresh air from the installed air introduction path to release the fuel vapor adsorbed on the activated carbon and introduce it into the intake pipe. This is a state in which the delay period has not passed since the prohibition.
State 3: When a brake booster using a negative pressure developed downstream of the throttle valve is provided, the brake switch is ON.
State 4: When a brake booster that uses negative pressure developed downstream of the throttle valve is provided, the delay period has not elapsed since the brake switch is turned off and the brake switch is turned off.
State 5: This cylinder distribution instability region is a cylinder distribution instability region when the engine load and the rotational speed are set in advance as parameters.
State 6: When the cylinder distribution unstable region is predetermined with the engine load and the engine speed as parameters, the cylinder distribution stable region is in the cylinder distribution stable region and the delay period has not elapsed. is there.
State 7: When a misfire determination function is provided, it is a misfire determination time.
State 8: When the misfire determination function is provided, the delay period has not elapsed since the misfire determination is canceled and the misfire determination is canceled.
State 9: EGR is being performed when an EGR device is provided.
State 10: In the case where an EGR device is provided, the delay period has not elapsed since EGR is prohibited and EGR is prohibited.
State 11: When a swirl control valve is provided, the delay period has not elapsed since the swirl control valve is closed or opened.
State 12: When an automatic transmission with a lockup mechanism is provided, the lockup is not in progress.
State 13: In the case where an automatic transmission with a lock-up mechanism is provided, the delay period has not elapsed since the lock-up and the lock-up.
State 14: When a fuel cut function is provided, the fuel is being cut.
State 15: When the fuel cut function is provided, the fuel cut is not being cut and the fuel cut is recovered -The delay period has not elapsed.
[0012]
  First3The invention44As shown, the means 51 for calculating the fuel supply amount according to the operating condition of the engine, the means 52 for supplying the supply amount of fuel to the engine, the means 53 for detecting the exhaust air-fuel ratio of the engine, The fuel supply amount is input, and the exhaust air / fuel ratio is output, and the means 54 for sampling the response waveform data of the exhaust air / fuel ratio with respect to the fuel supply amount with the currently used fuel and the input / output data are preliminarily constructed. By adjusting the parameters of the plant model so as to reduce the prediction error with respect to the reference model, means 61 for identifying the plant model for the fuel used, and the cut-off frequency fc of the identified plant model_Real, Means 81 for presetting the characteristic of the fuel property estimated value with respect to the cutoff frequency, and the calculated cutoff frequency fc_RealMeans for calculating an estimated fuel property value by searching for this characteristic, and a region where the exhaust air-fuel ratio fluctuates due to a factor other than the fuel propertyIs one of the following states 1 to 15And a region in which the exhaust air-fuel ratio fluctuates due to a factor other than the fuel property based on the determination result.Is one of the following states 1 to 15And means 57 for prohibiting the sampling of the input / output data.
State 1: The fuel vapor that evaporates in the fuel tank is guided to the canister and adsorbed on the activated carbon in the canister, the purge valve is opened under the purge ON condition, the suction negative pressure developed downstream of the throttle valve, and the canister In the case where a device is provided that uses fresh air from the air introduction path to separate the fuel vapor adsorbed on the activated carbon and introduces it into the intake pipe, the purge is being performed (when the purge valve is open).
State 2: The fuel vapor that evaporates in the fuel tank is guided to the canister and adsorbed to the activated carbon in the canister, the purge valve is opened when the predetermined operating condition is reached, the suction negative pressure developed downstream of the throttle valve, and the canister Purging is prohibited (when the purge valve is fully closed) and purged when equipped with a device that uses fresh air from the installed air introduction path to release the fuel vapor adsorbed on the activated carbon and introduce it into the intake pipe. This is a state in which the delay period has not passed since the prohibition.
State 3: When a brake booster using a negative pressure developed downstream of the throttle valve is provided, the brake switch is ON.
State 4: When a brake booster that uses negative pressure developed downstream of the throttle valve is provided, the delay period has not elapsed since the brake switch is turned off and the brake switch is turned off.
State 5: This cylinder distribution instability region is a cylinder distribution instability region when the engine load and the rotational speed are set in advance as parameters.
State 6: When the cylinder distribution unstable region is predetermined with the engine load and the engine speed as parameters, the cylinder distribution stable region is in the cylinder distribution stable region and the delay period has not elapsed. is there.
State 7: When a misfire determination function is provided, it is a misfire determination time.
State 8: When the misfire determination function is provided, the delay period has not elapsed since the misfire determination is canceled and the misfire determination is canceled.
State 9: EGR is being performed when an EGR device is provided.
State 10: In the case where an EGR device is provided, the delay period has not elapsed since EGR is prohibited and EGR is prohibited.
State 11: When a swirl control valve is provided, the delay period has not elapsed since the swirl control valve is closed or opened.
State 12: When an automatic transmission with a lockup mechanism is provided, the lockup is not in progress.
State 13: In the case where an automatic transmission with a lock-up mechanism is provided, the delay period has not elapsed since the lock-up and the lock-up.
State 14: When a fuel cut function is provided, the fuel is being cut.
State 15: When the fuel cut function is provided, the fuel cut is not being cut and the fuel cut is recovered -The delay period has not elapsed.
[0013]
  First4In the invention of the firstOr secondIn this invention, the estimation result of the fuel property is stored in a nonvolatile memory (for example, EEPROM).
[0014]
  First5In the invention of the3In the present invention, the estimated fuel property value is stored in a nonvolatile memory (for example, EEPROM).
[0015]
  First6In the invention of the1In the invention of claim 1, when the reference model is matched with a reference fuel, the estimation of the fuel property is lighter than the reference fuel when a cutoff frequency of the identified plant model is higher than a cutoff frequency of the reference model. It is estimated that.
[0016]
  First7In the invention of the2In the invention, when the estimation of the fuel property matches the reference model with a reference fuel, a difference between a cutoff frequency of the identified plant model and a cutoff frequency of the reference model is out of an allowable range, and When the cut-off frequency of the plant model is larger than the cut-off frequency of the reference model, it is estimated to be lighter than the reference fuel.
[0032]
  First8In the invention of the first2, 3, 5, 6, 7In any one of the inventions, adjusting the prediction error to be small is adjusting the prediction error to be minimum.
[0034]
  First9The invention45As shown in FIG. 5, the means 91 for supplying the engine with a fuel supply amount corresponding to the operating condition of the engine, the means 53 for detecting the exhaust air / fuel ratio of the engine, the fuel supply amount at the time of transition, and the exhaust air / fuel ratio being Means 54 for sampling the response waveform data of the exhaust air / fuel ratio with respect to the fuel supply amount at the currently used fuel as an output, and based on these input / output data, the parameters of the plant model constructed in advance are predicted errors from the reference model. Is adjusted so as to be small, and means 61 for identifying the plant model for the fuel used, and the cut-off frequency fc of the identified plant model_RealAnd a cut-off frequency fc of this plant model_RealAnd the cut-off frequency fc of the reference model_RefThe means 63 for estimating the fuel properties of the used fuel, the means 64 for calculating the fuel supply injection based on the estimation results of the fuel properties, and the exhaust air-fuel ratio fluctuate due to factors other than the fuel properties. Area to doIs one of the following states 1 to 15And a region in which the exhaust air-fuel ratio fluctuates due to a factor other than the fuel property based on the determination result.Is one of the following states 1 to 15And means 57 for prohibiting the sampling of the input / output data.
State 1: The fuel vapor that evaporates in the fuel tank is guided to the canister and adsorbed on the activated carbon in the canister, the purge valve is opened under the purge ON condition, the suction negative pressure developed downstream of the throttle valve, and the canister In the case where a device is provided that uses fresh air from the air introduction path to separate the fuel vapor adsorbed on the activated carbon and introduces it into the intake pipe, the purge is being performed (when the purge valve is open).
State 2: The fuel vapor that evaporates in the fuel tank is guided to the canister and adsorbed to the activated carbon in the canister, the purge valve is opened when the predetermined operating condition is reached, the suction negative pressure developed downstream of the throttle valve, and the canister Purging is prohibited (when the purge valve is fully closed) and purged when equipped with a device that uses fresh air from the installed air introduction path to release the fuel vapor adsorbed on the activated carbon and introduce it into the intake pipe. This is a state in which the delay period has not passed since the prohibition.
State 3: When a brake booster using a negative pressure developed downstream of the throttle valve is provided, the brake switch is ON.
State 4: When a brake booster that uses negative pressure developed downstream of the throttle valve is provided, the delay period has not elapsed since the brake switch is turned off and the brake switch is turned off.
State 5: This cylinder distribution instability region is a cylinder distribution instability region when the engine load and the rotational speed are set in advance as parameters.
State 6: When the cylinder distribution unstable region is predetermined with the engine load and the engine speed as parameters, the cylinder distribution stable region is in the cylinder distribution stable region and the delay period has not elapsed. is there.
State 7: When a misfire determination function is provided, it is a misfire determination time.
State 8: When the misfire determination function is provided, the delay period has not elapsed since the misfire determination is canceled and the misfire determination is canceled.
State 9: EGR is being performed when an EGR device is provided.
State 10: In the case where an EGR device is provided, the delay period has not elapsed since EGR is prohibited and EGR is prohibited.
State 11: When a swirl control valve is provided, the delay period has not elapsed since the swirl control valve is closed or opened.
State 12: When an automatic transmission with a lockup mechanism is provided, the lockup is not in progress.
State 13: In the case where an automatic transmission with a lock-up mechanism is provided, the delay period has not elapsed since the lock-up and the lock-up.
State 14: When a fuel cut function is provided, the fuel is being cut.
State 15: When the fuel cut function is provided, the fuel cut is not being cut and the fuel cut is recovered -The delay period has not elapsed.
[0035]
  First10The invention46As shown in FIG. 5, the means 91 for supplying the engine with a fuel supply amount corresponding to the operating condition of the engine, the means 53 for detecting the exhaust air / fuel ratio of the engine, the fuel supply amount at the time of transition, and the exhaust air / fuel ratio being Means 54 for sampling the response waveform data of the exhaust air / fuel ratio with respect to the fuel supply amount at the currently used fuel as an output, and based on these input / output data, the parameters of the plant model constructed in advance are predicted errors from the reference model. Is adjusted so as to be small, and means 61 for identifying the plant model for the fuel used, and the cut-off frequency fc of the identified plant model_RealAnd a cut-off frequency fc of this plant model_RealAnd the cut-off frequency fc of the reference model_RefThe difference 71 and the permissible range are compared to estimate the fuel properties of the fuel used, means 71 for calculating the fuel supply amount based on the estimation results of the fuel properties, and factors other than the fuel properties Region where exhaust air-fuel ratio fluctuatesIs one of the following states 1 to 15And a region in which the exhaust air-fuel ratio fluctuates due to a factor other than the fuel property based on the determination result.Is one of the following states 1 to 15And means 57 for prohibiting the sampling of the input / output data.
State 1: The fuel vapor that evaporates in the fuel tank is guided to the canister and adsorbed on the activated carbon in the canister, the purge valve is opened under the purge ON condition, the suction negative pressure developed downstream of the throttle valve, and the canister In the case where a device is provided that uses fresh air from the air introduction path to separate the fuel vapor adsorbed on the activated carbon and introduces it into the intake pipe, the purge is being performed (when the purge valve is open).
State 2: The fuel vapor that evaporates in the fuel tank is guided to the canister and adsorbed to the activated carbon in the canister, the purge valve is opened when the predetermined operating condition is reached, the suction negative pressure developed downstream of the throttle valve, and the canister Purging is prohibited (when the purge valve is fully closed) and purged when equipped with a device that uses fresh air from the installed air introduction path to release the fuel vapor adsorbed on the activated carbon and introduce it into the intake pipe. This is a state in which the delay period has not passed since the prohibition.
State 3: When a brake booster using a negative pressure developed downstream of the throttle valve is provided, the brake switch is ON.
State 4: When a brake booster that uses negative pressure developed downstream of the throttle valve is provided, the delay period has not elapsed since the brake switch is turned off and the brake switch is turned off.
State 5: This cylinder distribution instability region is a cylinder distribution instability region when the engine load and the rotational speed are set in advance as parameters.
State 6: When the cylinder distribution unstable region is predetermined with the engine load and the engine speed as parameters, the cylinder distribution stable region is in the cylinder distribution stable region and the delay period has not elapsed. is there.
State 7: When a misfire determination function is provided, it is a misfire determination time.
State 8: When the misfire determination function is provided, the delay period has not elapsed since the misfire determination is canceled and the misfire determination is canceled.
State 9: EGR is being performed when an EGR device is provided.
State 10: In the case where an EGR device is provided, the delay period has not elapsed since EGR is prohibited and EGR is prohibited.
State 11: When a swirl control valve is provided, the delay period has not elapsed since the swirl control valve is closed or opened.
State 12: When an automatic transmission with a lockup mechanism is provided, the lockup is not in progress.
State 13: In the case where an automatic transmission with a lock-up mechanism is provided, the delay period has not elapsed since the lock-up and the lock-up.
State 14: When a fuel cut function is provided, the fuel is being cut.
State 15: When the fuel cut function is provided, the fuel is not being cut. And fuel cut Rica The delay period has not elapsed from the bar.
[0036]
  First11The invention47As shown in FIG. 5, the means 91 for supplying the engine with a fuel supply amount corresponding to the operating condition of the engine, the means 53 for detecting the exhaust air / fuel ratio of the engine, the fuel supply amount at the time of transition, and the exhaust air / fuel ratio being Means 54 for sampling the response waveform data of the exhaust air / fuel ratio with respect to the fuel supply amount at the currently used fuel as an output, and based on these input / output data, the parameters of the plant model constructed in advance are predicted errors from the reference model. Is adjusted so as to be small, and means 61 for identifying the plant model for the fuel used, and the cut-off frequency fc of the identified plant model_Real, Means 81 for presetting the characteristic of the fuel property estimated value with respect to the cutoff frequency, and the calculated cutoff frequency fc_RealMeans 82 for calculating the fuel property estimated value by searching for this characteristic, means 83 for calculating the fuel supply amount based on the estimated fuel property value, and the exhaust air-fuel ratio fluctuates due to factors other than the fuel property. AreaIs one of the following states 1 to 15And a region in which the exhaust air-fuel ratio fluctuates due to a factor other than the fuel property based on the determination result.Is one of the following states 1 to 15And means 57 for prohibiting the sampling of the input / output data.
State 1: The fuel vapor that evaporates in the fuel tank is guided to the canister and adsorbed on the activated carbon in the canister, the purge valve is opened under the purge ON condition, the suction negative pressure developed downstream of the throttle valve, and the canister In the case where a device is provided that uses fresh air from the air introduction path to separate the fuel vapor adsorbed on the activated carbon and introduces it into the intake pipe, the purge is being performed (when the purge valve is open).
State 2: The fuel vapor that evaporates in the fuel tank is guided to the canister and adsorbed to the activated carbon in the canister, the purge valve is opened when the predetermined operating condition is reached, the suction negative pressure developed downstream of the throttle valve, and the canister Purging is prohibited (when the purge valve is fully closed) and purged when equipped with a device that uses fresh air from the installed air introduction path to release the fuel vapor adsorbed on the activated carbon and introduce it into the intake pipe. This is a state in which the delay period has not passed since the prohibition.
State 3: When a brake booster using a negative pressure developed downstream of the throttle valve is provided, the brake switch is ON.
State 4: When a brake booster that uses negative pressure developed downstream of the throttle valve is provided, the delay period has not elapsed since the brake switch is turned off and the brake switch is turned off.
State 5: This cylinder distribution instability region is a cylinder distribution instability region when the engine load and the rotational speed are set in advance as parameters.
State 6: When the cylinder distribution unstable region is predetermined with the engine load and the engine speed as parameters, the cylinder distribution stable region is in the cylinder distribution stable region and the delay period has not elapsed. is there.
State 7: When a misfire determination function is provided, it is a misfire determination time.
State 8: When the misfire determination function is provided, the delay period has not elapsed since the misfire determination is canceled and the misfire determination is canceled.
State 9: EGR is being performed when an EGR device is provided.
State 10: In the case where an EGR device is provided, the delay period has not elapsed since EGR is prohibited and EGR is prohibited.
State 11: When a swirl control valve is provided, the delay period has not elapsed since the swirl control valve is closed or opened.
State 12: When an automatic transmission with a lockup mechanism is provided, the lockup is not in progress.
State 13: In the case where an automatic transmission with a lock-up mechanism is provided, the delay period has not elapsed since the lock-up and the lock-up.
State 14: When a fuel cut function is provided, the fuel is being cut.
State 15: When the fuel cut function is provided, the fuel cut is not being cut and the fuel cut is recovered -The delay period has not elapsed.
[0037]
  First12In the invention of the9th or 10thIn this invention, the estimation result of the fuel property is stored in a nonvolatile memory (for example, EEPROM).
[0038]
  First13In the invention of the11In the present invention, the estimated fuel property value is stored in a nonvolatile memory (for example, EEPROM).
[0039]
  First14In the invention of the9In the invention of claim 1, when the reference model is matched with a reference fuel, the estimation of the fuel property is lighter than the reference fuel when a cutoff frequency of the identified plant model is higher than a cutoff frequency of the reference model. It is estimated that.
[0040]
  First15In the invention of the10In the invention, when the estimation of the fuel property matches the reference model with a reference fuel, a difference between a cutoff frequency of the identified plant model and a cutoff frequency of the reference model is out of an allowable range, and When the cut-off frequency of the plant model is larger than the cut-off frequency of the reference model, it is estimated to be lighter than the reference fuel.
[0056]
  First16In the invention of the9, 10, 11th, 13th, 14th, 15thIn any one of the inventions, adjusting the prediction error to be small is adjusting the prediction error to be minimum.
[0057]
【The invention's effect】
FirstAccording to the present invention, the parameter of the plant model is set so that the prediction error with the reference model is reduced, and8The second16According to the invention, the plant model is identified by adjusting the parameter of the plant model so that the prediction error with the reference model is minimized. The transfer function of the plant model is known from the parameters at this time, and the cutoff frequency of the plant model is determined from this.
[0058]
Here, when the reference model is matched with the reference fuel and the fuel used is lighter than the reference fuel, the cutoff frequency of the plant model is higher than that for the reference fuel (and vice versa). When the fuel used is heavier than the reference fuel, the cutoff frequency of the plant model is lower than that for the reference fuel). This is because the lighter fuel than the reference fuel has a smaller fuel transport delay than the reference fuel, so that the fuel response becomes higher and the response gain can be maintained up to a higher frequency range than the reference fuel.
[0059]
  Therefore, the second1The second9According to this invention, it is possible to estimate the fuel property of the fuel used by comparing the cutoff frequency of the plant model with the cutoff frequency of the reference model. For example,6The second14When the reference model is matched to the reference fuel as in the invention of the invention, when the cut-off frequency of the identified plant model is higher than the cut-off frequency of the reference model,7The second15When the reference model is matched to the reference fuel as in the invention of, the difference between the identified plant model cutoff frequency and the reference model cutoff frequency is outside the allowable range, and the plant model cutoff is When the frequency is higher than the cut-off frequency of the reference model, the fuel used may be estimated to be lighter than the reference fuel. In this way, when it is possible to estimate the fuel properties, this is utilized in the calculation of the fuel supply amount.15According to this invention, it is possible to give the fuel supply amount according to the fuel property of the fuel used without excess or deficiency.
[0060]
  On the other hand, if the exhaust air / fuel ratio fluctuates due to factors other than fuel properties, sampling the exhaust air / fuel ratio as output data will result in inaccurate data. If the fuel properties are estimated based on this inaccurate data, Although the accuracy is reduced, FirstThe second9The second6The second14The second7The second15The second8The second16According to the invention, in this case, by prohibiting the sampling of the input / output data, it is possible to avoid the deterioration of the estimation accuracy of the fuel property.
[0061]
  First2The second10According to this invention, even if the cut-off frequency with respect to the reference fuel varies, it is possible to stably estimate the fuel properties.
[0062]
  First3The second11According to this invention, the calculation accuracy of the fuel supply amount can be improved.
[0063]
  First4The second5The second11The second12According to this invention, the estimation result of the fuel property and the estimated value of the fuel property can be used from the beginning of the start at the next operation.
[0064]
  1st, 2nd, 3rd, 9th, 10th, 11thAccording to this invention, the estimation accuracy of the fuel property does not decrease even in an engine including a so-called evaporated fuel processing device.
[0065]
  1st, 2nd, 3rd, 9th, 10th, 11thAccording to this invention, the estimation accuracy of the fuel property is not lowered even in the vehicle including the brake booster that uses the negative pressure developed downstream of the throttle valve.
[0066]
  1st, 2nd, 3rd, 9th, 10th, 11thAccording to this invention, the estimation accuracy of the fuel property does not decrease even in an engine in which the cylinder distribution unstable region is determined in advance using the engine load and the rotational speed as parameters.
[0067]
  1st, 2nd, 3rd, 9th, 10th, 11thAccording to this invention, the estimation accuracy of the fuel property does not deteriorate even in an engine having a misfire determination function.
[0068]
  1st, 2nd, 3rd, 9th, 10th, 11thAccording to the invention, the estimation accuracy of the fuel property is not lowered even in the engine including the EGR device.
[0069]
  1st, 2nd, 3rd, 9th, 10th, 11thAccording to this invention, the estimation accuracy of the fuel property does not deteriorate even in an engine having a swirl control valve.
[0070]
  1st, 2nd, 3rd, 9th, 10th, 11thAccording to this invention, the estimation accuracy of the fuel property is not lowered even in a vehicle including an automatic transmission with a lockup mechanism.
[0071]
  1st, 2nd, 3rd, 9th, 10th, 11thAccording to the invention, the estimation accuracy of the fuel property is not lowered even in the engine having the fuel cut function.
[0072]
DETAILED DESCRIPTION OF THE INVENTION
In FIG. 1, reference numeral 1 denotes an engine body, and intake air is supplied from an air cleaner through an intake pipe 8 to a cylinder. The fuel is injected from the fuel injection valve 7 toward the intake port of the engine 1 based on an injection signal from the ECM 2 so as to have a predetermined air-fuel ratio according to the operating conditions.
[0073]
The ECM 2 includes a REF signal from the crank angle sensor 4 (a signal for identifying a cylinder generated every 180 ° for four cylinders and every 120 ° for six cylinders), a 1 ° signal, and an intake air amount signal from the air flow meter 6. , An air-fuel ratio signal from a wide-range air-fuel ratio sensor (hereinafter simply referred to as “A / F sensor”) 3 installed on the upstream side (exhaust manifold assembly) of the three-way catalyst 10, a cooling water temperature signal from the water temperature sensor 11, a throttle sensor Based on these, the ECM 2 calculates the basic injection pulse width Tp from the intake air amount Qa and the engine speed Ne, and transiently corrects this Tp during acceleration / deceleration. Correction for wall flow fuel is performed by adding the amount Kathos. The transient correction amount Kathos works not only at the time of acceleration / deceleration, but also at the time of start-up when the wall flow fuel changes greatly, at the time of fuel recovery, and at the time of switching a target equivalent ratio Tfbya described later.
[0074]
The ECM 2 also performs fuel correction using the target equivalence ratio Tfbya in order to improve engine stability during cold start and respond to the required output at high load, as well as a gear position signal from the gear position sensor 13 of the transmission, The lean air-fuel ratio and the stoichiometric air-fuel ratio are controlled according to the conditions while judging the driving state based on a vehicle speed signal from a vehicle speed sensor (not shown). A three-way catalyst 10 is installed in the exhaust pipe 9 to reduce NOx in the exhaust and oxidize HC and CO with maximum conversion efficiency during operation at the stoichiometric air-fuel ratio. When the three-way catalyst 10 has a lean air-fuel ratio, HC and CO are oxidized, but NOx reduction efficiency is low. However, the more the air-fuel ratio shifts to the lean side, the smaller the amount of NOx generated. When the air-fuel ratio exceeds a predetermined air-fuel ratio, it can be reduced to the same level as that purified by the three-way catalyst 10, and at the same time the lean air-fuel ratio. The better the fuel economy is. Therefore, in a predetermined operation region where the load is not so large, the target equivalence ratio Tfbya is set to a value smaller than 1.0, and the lean air-fuel ratio is operated, and in other operation regions, Tfbya is set to 1.0. Thus, the air-fuel ratio is controlled to the stoichiometric air-fuel ratio.
[0075]
As described above, the target equivalent ratio Tfbya is switched according to the change in the operating condition. However, if the above transient correction amount Kathos is calculated as a value for Tfbya = 1.0 (that is, the theoretical air-fuel ratio), the output When switching from Tfbya, such as when decelerating from the air-fuel ratio range (Tfbya is greater than 1.0 at this time), the transient correction amount Katos becomes insufficient, causing the air-fuel ratio to temporarily become overrich or overlean, and the control air-fuel ratio In order to cope with this, the followability deteriorates. In ECM2, the equilibrium adhesion amount Mfh is calculated using the target equivalent ratio Tfbya as a parameter. If this is expressed by an arithmetic expression,
Mfh = Avtp × Mfhtvo × Tfbya × CYLDRN #
Where Mfh: the amount of equilibrium adhesion for all cylinders,
Avtp: injection valve part air amount equivalent pulse width,
Mfhtvo: Adhesion magnification,
CYLDRN #: Number of cylinders
(See Japanese Patent Laid-Open No. 10-18882). The difference between the equilibrium adhesion amount (the equilibrium value of the wall flow fuel) Mfh and the current adhesion amount Mf is multiplied by the quantity ratio Kmf, that is,
Vmf = (Mfh−Mf) × Kmf
The deposition rate (the amount of deposition per unit cycle) Vmf (value per cycle) is calculated by the following formula. When the equilibrium deposition amount Mfh increases (for example, during acceleration), this is set as a transient correction amount Kathos.
CTIn = (Avtp × Tfbya + Kathos) × α × 2 + Ts + Chosn¹
However, Kathos: transient correction amount (value per cycle),
α: Air-fuel ratio feedback correction coefficient,
Ts: Invalid injection pulse width,
Chosn¹: Cylinder wall flow correction amount (value per cycle for each cylinder),
The actual injection pulse width CTIn given to the fuel injection valve at the time of sequential injection (in the case of four cylinders, once every two engine revolutions, in accordance with the ignition order of each cylinder) is calculated for each cylinder. The “value for each cycle” is a value for each input of the 1REF signal, and the “value for each cycle of each cylinder” is a value for each input of the 4REF signal (in the case of 4 cylinders). CTIn and Chosn¹“N” represents a cylinder number.
[0076]
Here, the cylinder-specific wall flow correction amount Chosn will be described. The wall flow fuel has a small amount of direct flow into the cylinder and is relatively slow in response (referred to as a low frequency component), and directly into the cylinder. There is a part that is mainly responsive (referred to as a high-frequency component), and the above Vmf is a wall flow correction amount targeting a low-frequency component, whereas Chosn is a correction targeting a high-frequency component. Amount. That is, since Vmf alone cannot cope with high frequency components, it is necessary to introduce Chosn, which is a correction amount for high frequency components. Specifically, if Avtp is increasing (during acceleration) using ΔAvtpn, which is the amount of change in the injection valve portion air amount equivalent pulse width Avtp from the previous injection,
Chosn = ΔAvtpn × Gztwp
Where Gztwp: increase gain,
When Avtp is decreasing (during deceleration)
Chosn = ΔAvtpn × Gztwm
Where Gztwm: weight loss gain,
The wall flow correction for the high-frequency component is performed by adding the value to the fuel injection pulse width of the synchronous injection for each cylinder. The increase gain Gztwp and the decrease gain Gztwm are for performing water temperature correction. Further, n attached at the end of ΔAvtpn represents the cylinder number as in the case of CTIn.
[0077]
Even in the case where the wall flow correction amount for the high frequency component is introduced in addition to the wall flow correction amount for the low frequency component as described above, if Tfbya is not taken into account in Chosn calculation, particularly from the output air-fuel ratio range. Since Chosn becomes deficient when Tfbya is switched such as when decelerating and temporarily overrich or overlean occurs, ECM2 also deals with Chosn, which is a wall flow correction amount for high-frequency components, in accordance with Tfbya. (Refer to Japanese Patent Laid-Open No. 10-18882). If this is expressed by an arithmetic expression,
Chosn¹= (Kathos-Kathos_-4Ref) × (Gztwc-1) / A
However, Chosn¹: Chosn in the first cycle,
Kathos_-4Ref: Kathos 1 cycle before each cylinder (before 4REF signal),
Gztwc: increase gain Gztwp or decrease gain Gztwm,
A: Response gain of the first cycle of the low frequency component,
It is.
[0078]
It should be noted that the amount of wall flow correction (Chosn) at the time of fuel recovery in consideration of fuel cut (fuel cut may be performed for each cylinder or may be performed simultaneously for all cylinders)¹, Vmf), an optimal wall flow correction amount may be given even during fuel recovery accompanied by switching of the target equivalent ratio Tfbya (see Japanese Patent Laid-Open No. 10-18882).
[0079]
On the other hand, at the time of cold start when the engine becomes unstable, the fuel is increased by the post-startup increase correction coefficient KAS, and the engine is stabilized by setting the air-fuel ratio to a richer value than the stoichiometric air-fuel ratio (Japanese Patent Laid-Open No. Hei. 6-101529). For example, KAS is calculated according to equation 36, which will be described later. At this time, KAS roughly decreases linearly with a steep slope from the start timing of the starter switch, with the value when the starter switch is turned on as an initial value. From, it becomes a gentle slope and decreases, and finally becomes 0.
[0080]
The post-startup increase correction coefficient KAS is a part of the target equivalent ratio Tfbya. For example,
Tfbya = Kml + KAS
Where Dml: fuel-air ratio correction coefficient,
The target equivalent ratio Tfbya is calculated by the following formula.
[0081]
Here, Kml determines a target air-fuel ratio according to operating conditions, and is obtained by searching a map using the engine speed and load as parameters. In some cases, when a target air-fuel ratio is switched, a predetermined damper operation is performed after retrieving a map value of Kml.
[0082]
Further, a special fuel injection pulse width TIST is set at the time of starting (see Japanese Patent Laid-Open No. 7-63082). When a particularly large torque is required, such as during rapid acceleration, the acceleration interrupt injection pulse width IJSETn is calculated, and interrupt injection may be performed even during synchronous injection.
[0083]
The reason why various injection amount corrections such as the above KAS are necessary is that a fuel supply delay corresponding to the wall flow fuel occurs, but this wall flow fuel amount further increases the fuel properties (particularly volatile). In other words, the fuel with lower volatility increases the amount of wall flow fuel. Taking into account the difference in fuel flow due to the difference in fuel volatility, various conventional injection amount corrections (for example, conventional post-startup increase corrections) can be used even when the heaviest gasoline is used. Data used for the calculation of KAS is matched so that the rotation does not become unstable.
[0084]
However, when fuel with better volatility than the heaviest gasoline is used, various injection amount correction amounts become too large, and this makes the actual air-fuel ratio target value expected when using the heaviest gasoline. Since the air-fuel ratio is inclined to the rich side, exhaust emission (especially CO, HC) is deteriorated.
[0085]
Therefore, at the time of transition in a region where the wall flow fuel amount is large, the response waveform of the exhaust air / fuel ratio with respect to the fuel injection amount is sampled, and the parameters of the plant model previously built on the ECM 2 based on the data at the time of transition are defined as the reference model and The plant model is identified by adjusting the estimation error so that the estimation error is minimized, the cut-off frequency of the plant model is obtained based on the adjusted parameter, and the norm that is the plant model for the reference fuel (Ref fuel) A fuel property is estimated by comparing with the cut-off frequency of the model, and various injection amount correction amounts are calculated in accordance with the estimated fuel property.
[0086]
On the other hand, even if the exhaust air-fuel ratio changes due to factors other than fuel properties even during a transition, sampling the input / output data will result in inaccurate data and lower fuel property estimation accuracy. When the exhaust air-fuel ratio fluctuates due to factors other than the properties, sampling of input / output data is prohibited.
[0087]
This optimization control executed in ECM2 will be described next.
[0088]
FIG. 2 is a block diagram of a control system for optimization control.
[0089]
This control system is roughly divided into a plant identification unit 21, a fuel property estimation unit 22, a triggering function 23, and a controller 24.
[0090]
The outline of the control will be described with reference to FIG. 2 and then plant identification will be described in detail.
[0091]
First, main components of the plant identification unit 21 are a plant model 31, an error detection unit 32, an optimization calculation unit 33, an input (actual injection pulse width) buffering unit 34, and an output (exhaust air / fuel ratio) buffering. The actual injection pulse width CTIn and the A / F sensor 3 output voltage are sampled from the trigger determined from the engine parameters, and the plant model 31 in that region is used as an input / output signal of the plant model 31. Identification. The model format (order) is set in advance from the physical model, and the model parameters are adjusted so as to be optimal for actual input / output signals.
[0092]
Here, the plant model 31 is a discrete cascade coupling model (a denominator 3 having a denominator secondary and denominator second-order lag system model and an exhaust dynamic characteristic being a denominator first-order lag system model. Next, a molecular tertiary physical model). The identification method is a batch process least square method using the most common ARX model.
[0093]
The fuel property estimation unit 22 includes a reference model 37 that is a plant model with respect to a reference fuel (Ref fuel), and a cutoff frequency comparison unit 38, and a cutoff frequency fc of the plant model 31 identified by the plant identification unit 21._RealAnd the cut-off frequency fc of the reference model 37_RefIs compared by the comparison means 38 to determine the fuel property.
[0094]
Here, for simplicity of explanation, if there are only two types of fuel (heavier gasoline with lower volatility is assumed to be heavy gasoline and lighter fuel with better volatility is assumed to be light gasoline) When the reference model matched with gasoline is used, when the cut-off frequency of the identified plant model 31 is higher than the cut-off frequency of the reference model, it can be determined that light gasoline is being used. This is because light gasoline has a smaller fuel transport delay than heavy gasoline, and light gasoline has higher fuel responsiveness and can maintain a response gain up to a higher frequency range than heavy gasoline. Note that the fuel property determination value is initially set to heavy gasoline before the fuel property is estimated.
[0095]
In this control, the fuel property is estimated once, for example, during one trip (from the start to the stop of the engine operation), and the estimation result is stored in a non-volatile memory (in this embodiment, EEPROM 14, see FIG. 1). The controller 24 reflects this in the fuel control at the next start.
[0096]
The triggering function 23 samples input / output signals necessary for plant identification and determines a condition for generating a trigger for starting plant identification.
[0097]
Here, in general, in order to identify a system, an input including a wide frequency band is required. In the engine, since it is not realistic to generate an input such as an M-sequence, a point where the input changes stepwise is set as a sampling trigger. It is also necessary to eliminate conditions that greatly affect fuel behavior such as EGR (exhaust gas recirculation) and swirl control. Conditions as described above must exist in the mode for identification or generate an input signal for identification.
[0098]
Specifically, the controller 24 is a post-startup increase correction coefficient adjusting means that sets the post-startup increase correction amount KAS immediately after the next start to an appropriate value according to the fuel property estimated during one trip. Items to be adjusted are the initial value of KAS and the attenuation ratio.
[0099]
Here, for simplification of the control as described above, description will be made with binary switching for heavy gasoline or light gasoline (the post-startup increase correction coefficient adjusting means is therefore the post-startup increase correction coefficient switching means 40. Therefore, the number of stages for switching the fuel property may be determined from the separation performance of the fuel property and the requirements of the engine.
[0100]
The fuel injection amount calculation means 15 is used for Vmf, CTIn, Chosn described above.¹Is calculated.
[0101]
Next, the identification of the plant model 31 will be described in detail with separate terms.
[0102]
1. Plant model
In order to estimate the fuel properties, it is necessary to extract only the dynamics of the fuel behavior from the dynamics of the engine. The 4-cycle engine (plant) is considered to be composed of the elements shown in FIG. The input / output that can be observed is the actual injection pulse width CTIn obtained by calculating the basic injection pulse width Tp based on the intake air amount Qa and performing various corrections on the basic injection pulse width Tp. IJSETn at the time of interruption injection) and the A / F sensor output value of the exhaust manifold aggregate part subjected to A / D conversion. The plant model obtained from this input / output is
1.1: Fuel behavior model (dead time + delay system),
1.2: Exhaust model (dead time + delay system) and
1.3: Waste time depending on various operations and combustion cycle
It consists of three.
[0103]
1.1 Fuel behavior model
The behavior of the fuel injected from the fuel injection valve can be modeled as shown in FIG. 4 and the mathematical model is expressed as follows.
[0104]
[Expression 1]
F_fc= (1-k_WW) ・ F_fi+ F_fe
F_fe= E^{-t / TWW}・ K_WW・ F_fi/ T_WW
G_WW(s) = (1-k_WW) + K_WW/ (ST_WW+1)
However, G_WW: Transfer function of fuel behavior,
F_fi: Fuel injection,
F_fe: Fuel evaporation,
F_fc: Cylinder intake fuel,
k_WW: Adhesion rate,
T_WW: Time constant of evaporation,
This mathematical model has one time constant (T_WW) And one gain (k_WWHowever, the behavior of fuel is generally divided into a time constant due to fuel adhesion and evaporation and a time constant due to cylinder suction delay. In terms of the above expression, the slower the response, the lower the frequency. The component and the faster the response are high frequency components.
[0105]
Therefore, the mathematical model of Equation 1 may be connected in parallel for the behavior of two types of fuels with different responses. The mathematical model at this time can be expressed as follows.
[0106]
[Expression 2]

Where Tsample: sampling period (period for sampling the air-fuel ratio),
T₁: Time constant of low frequency component,
T₂: Time constant of high frequency component,
k₁: Gain of low frequency component,
k₂: Gain of high frequency component,
A₁: E^{-Tsample / T1},
A₂: E^{-Tsample / T2},
B₁: K₁,
B₂: K₂,
In Formula 2, the first formula (continuous value system) converted to the discrete value system is the second formula, and this second formula is expressed as z = e^sTsampleThe third formula is obtained by substituting and organizing. FIG. 5 is a block diagram showing the third equation.
[0107]
The dead time associated with the fuel behavior is not taken into the mathematical model of the fuel behavior, and the output signal is offset in time series to suppress the increase in the model order (details will be described later in 1.3).
[0108]
1.2 Exhaust model
As shown in FIG. 6, the exhaust model is considered to be composed of three elements: exhaust dynamics for each cylinder, gas mixing dynamics in the exhaust manifold assembly, and sensor characteristics. When these are combined, they can be represented by a physical model of “dead time + delay system”. As the delay system, exhaust gas transport delay + gas mixing delay + sensor response delay can be considered, and each is a model having a first-order delay or more. However, considering that the plant model is identified on board (on the ECM2) this time, it is necessary to avoid being higher order as much as possible. As an exhaust model, it is represented by one time constant, and 1 Describe with a mathematical model of the next delay system.
[0109]
[Equation 3]
G_ex(s) = 1 / (sT_ex+1)
G_ex(z) = (1-e^{-Tsample / Tex}) / (Ze^{-Tsample / Tex})
G_ex(z) = (1-A_Three) / (Z-A_Three)
However, G_ex: Transfer function of exhaust dynamic characteristics,
T_ex: Evaporation time constant,
Tsample: sample period,
A_Three: E^{-Tsample / Tex},
Also in Equation 3, the first equation converted into a discrete value system is the second equation and the second equation z = e^sTsampleThe third formula is obtained by substituting and organizing.
[0110]
In addition, the dead time is offset in time series like the fuel behavior model, and is not taken into the exhaust model (described later in 1.3).
[0111]
1.3 Waste time model
Since this plant model 31 has an actual injection pulse width CTIn as an input and an output voltage read value of the A / F sensor 3 as an output, as shown in FIG. There is some dead time (indicated by “Delay” in the figure) before the ECM 2 reads the F sensor output value. Therefore, the dead time between input and output is shown again in detail in FIG.
[0112]
Here, each dead time will be described.
[0113]
1) Delay1: Delay from injection amount calculation to actual injection timing,
The actual injection pulse width CTIn is calculated every 10 ms, and is not necessarily the same every cycle until the actual fuel injection timing. The dead time Delay 1 is obtained by calculating the time from the pulse width calculation timing from the calculated injection timing (fuel injection start) angle and the rotation speed at that time.
[0114]
2) Delay 2: Delay from actual injection timing to IVO (intake valve open)
This is the time from when the fuel is injected until the intake valve is opened and the fuel is sucked into the cylinder. This delay is determined by the fuel behavior characteristics and is set according to each operating condition and fuel properties. For example, using commercially available fuel that is almost in the middle of volatility, changing the fuel stepwise for each operating condition (for example, engine speed and load) and measuring the response time is appropriate. Set a correct value.
[0115]
3) Delay 3: Delay from IVO to EVO (exhaust valve open) (intake → compression → combustion → exhaust),
This is the time from when the fuel is drawn into the cylinder through the intake valve until the combustion gas is discharged from the exhaust valve. This delay can be obtained from the rotational speed and the cam profile, and is obtained from the design specifications.
[0116]
4) Delay 4: Delay from when the combustion gas leaves the exhaust valve until it reaches the A / F sensor,
This is the time from when the combustion gas in the cylinder is discharged from the exhaust valve until it reaches the A / F sensor section through the exhaust pipe. It is set according to the exhaust flow velocity (depending on the number of revolutions, load, etc.), the exhaust length, the A / F sensor mounting position, etc. In addition, although calculation becomes complicated, you may obtain | require from an operating condition and a hardware specification.
[0117]
5) Delay5: Sensor response delay,
This is the time from when the gas reaches the A / F sensor section until the A / F sensor outputs a voltage. When the oxygen amount fluctuates, the A / F sensor itself reacts in a few ms, but the gas mixing delay due to the sensor cover is dominant, and the time varies greatly depending on the shape of the sensor cover. For this reason, this delay is set to an appropriate value in the same manner as Delay 4.
[0118]
6) Delay 6: Delay until the sensor output value is A / D converted and loaded into ECM 2.
This is a delay caused by performing A / D conversion in order to capture the voltage output from the A / F sensor into the ECM 2. In the current hardware configuration, A / D conversion of the A / F sensor 3 is performed every 2 ms, and the maximum dead time is 2 ms.
[0119]
7) Delay 7: Delay until the sensor output value is buffered in the memory.
When the A / F sensor output value is sampled at 10 ms, there is a possibility that a maximum dead time of 10 ms may occur depending on the sampling timing. Therefore, the dead time from the response start to the sampling timing calculated from the A / D converted value in 2 ms is calculated as Delay7.
[0120]
8) Delay8: Variation
This is a variation that occurs in addition to the dead time obtained from Delays 1-7. Variations between models, variation in conformity, and the like are conceivable and are uncertain for each operation. Therefore, the rise of the air-fuel ratio signal after the delays 1 to 7 are determined and determined.
[0121]
This completes the explanation of each dead time.
[0122]
When the above Delays 1 to 8 are analyzed, the wasted time is
(1) Terms determined by operating conditions
(2) Matters determined from calculation timing,
(3) Terms that vary depending on fuel properties
(See FIG. 8). Therefore, the actual dead time can be expressed by the following equation.
[0123]
Wasted time
= Applicable terms (determined by operating conditions, table or map search)
+ Calculation term (determined from calculation timing, calculation using timing signal, etc.)
+ Judgment term (determined as necessary due to variations in fuel properties, etc.)
2. Plant model identification
2.1 Creating a model to identify
Although an actual engine has a strong non-linearity, it is assumed in this control that it is a so-called linear time-invariant system (LTI) that is linear and time-invariant near a certain operating point.
[0124]
In addition, since the discrete-time LTI system describes input / output in the time domain instead of the Z domain, the shift operator q^-1Is defined as follows.
[0125]
[Expression 4]
q^-1x (k) = x (k-1)
However, discrete time = kT (T: sampling period, k = 0, 1, 2,...).
[0126]
Using this, a system transfer function of an input u (t) and an output y (t) of a discrete value system is described.
[0127]
[Equation 5]
y (k) = G (q, θ) · u (k)
It becomes. θ is composed of parameters describing the model. However, this is an ideal input / output, and considering external noise,
[0128]
[Formula 6]
y (k) = G (q, θ) · u (k) + H (q, θ) · w (k)
Can be described. Here, H (q, θ) is a noise model, and a general discrete-time LTI system can be expressed by Equation 6. A block diagram of the system is shown in FIG.
[0129]
Here, the transfer function G (q) of the system is the product of the third equation of Equation 2 and the third equation of Equation 3, and Z^-1Is the shift operator q^-1Which is described in
[0130]
[Expression 7]

It can be expressed. The transfer function G (q) of this system is
[0131]
[Equation 8]
G (q, θ) = B (q, θ) / A (q, θ)
The system output value y (k) is defined as
[0132]
[Equation 9]
y (k, θ) = {B (q, θ) / A (q, θ)} · u (k) + H (q, θ) · w (k)
It can be expressed as. Thus, as a model to identify, what combined G (q) which is a plant model, and H (q) which is a noise model in the appropriate form is employ | adopted.
[0133]
2.2 Identification method
In the discrete-time LTI system defined by Equation 6, the one-step predicted value y (k | θ) of the output y (k) based on the input / output data measured up to time (k−1) is
[0134]
[Expression 10]
y (k | θ) = [1-H^-1(q, θ)] y (k) + H^-1(q, θ) G (q, θ) u (k)
It is expressed by the following formula. Thereby, the output at time k can be described by the data acquired up to (k−1).
[0135]
The prediction error ε (k | θ) is
[0136]
## EQU11 ##
ε (k | θ) = y (k) −y (k | θ)
It can be expressed by the following formula.
[0137]
Now, the evaluation criteria J for parameter estimation_N(θ)
[0138]
[Expression 12]

Set. Here, the function l (k, θ, ε (k, θ)) is an arbitrary scalar value function for measuring the magnitude of the prediction error ε (k, θ), and what norm to select is identified. Depends on the purpose of the result (square norm, log likelihood, etc.) By defining such an evaluation criterion, an estimated value of unknown parameter θ (referred to as θ (N)) is determined. That means
[0139]
[Formula 13]

Is to obtain θ.
[0140]
In general, various methods have been proposed as an identification method, but an engine-like object is an intermittent event (combustion cycle or the like), and is a control object with very strong nonlinearity. However, this control assumes a linear time invariant (LTI) system around the operating point to simplify the algorithm.
[0141]
This time, in consideration of the small amount of calculation, the identification accuracy, and the disturbance performance, the “collective identification method using the ARX model, which is parametric model identification”, which is a representative linear model identification method, is adopted.
[0142]
2.3 Identification method of ARX model
The ARX model is called an equation error model, and a disturbance term e (k) (assumed as white noise in the ARX model and assumed as w (k)) is entered on the right side of the difference equation as follows.
[0143]
[Expression 14]

The parameter vector θ describing the model is
[0144]
[Expression 15]
θ = [a₁, ..., a_na, B₁, ..., b_nb]^T
It becomes. Data vector (regression vector) ψ (k)
[0145]
[Expression 16]
ψ (k) = [− y (k−1),..., −y (k−na), u (k−1),..., u (k−nb)]^T
The output y (k) can be expressed as follows:
[0146]
[Expression 17]
y (k) = θ^Tψ (k) + w (k)
The one-step predicted value y (k | θ) of the ARX model is linear with respect to θ when calculated from Equation 10.
[0147]
[Expression 18]
y (k | θ) = θ^Tψ (k)
It is expressed. The prediction error ε (k, θ) at this time is
[0148]
[Equation 19]
ε (k, θ) = y (k) −θ^Tψ (k)
Can be expressed as When the least square method is applied to this linear regression model, the scalar value function l (k, θ, ε (k, θ)) is
[0149]
[Expression 20]
l (k, θ, ε (k, θ)) = ε²(k, θ)
The parameter estimation evaluation norm J_N(θ) is
[0150]
[Expression 21]

It becomes. Further calculating equation (21)
[0151]
[Expression 22]

[0152]
[Expression 23]
J_N(θ) = c (N) −2θ^Tf (N) + θ^TR (N) θ
It can be said.
[0153]
However, c (N), f (N), and R (N) in Equation 23 are as follows.
[0154]
[Expression 24]

[0155]
[Expression 25]

[0156]
[Equation 26]

Evaluation standard J_N(θ) is minimized when J_NSince (θ) is a quadratic function related to θ, if the highest order coefficient is positive, J_NThis is where the differential value of (θ) becomes zero. When the differential value of Equation 23 is set to 0, the following normal equation (simultaneous linear equation relating to θ) is obtained.
[0157]
[Expression 27]

Thus, if R (N) is a positive definite matrix, J_N(θ) is the minimum when the differential value is zero (J_N(θ) is a downward convex function, see FIG.
[0158]
[Expression 28]

The parameter θ (N) can be estimated by the following equation. The above identification procedure is shown in FIG.
[0159]
There are the following three conditions for the positive definite matrix.
[0160]
1) When the identification target is n-th order, the input signal u (k) must include n or more sine waves (a sufficient frequency component is included in the step input signal).
[0161]
2) The identification target is stable (the engine can be considered as a stable system in a steady state).
[0162]
3) The identification target is observable. That is, A (q, θ) and B (q, θ) do not have a common factor (since this model is a discrete system, B (q, θ) has a higher order, but there is no problem).
[0163]
2.4 Identification of the actual ARX model
This model is a discrete system model of denominator 3rd order and numerator 3rd order from Equation 7.
[0164]
[Expression 29]
A (q) = 1 + a₁・ Q^-1+ A₂・ Q^-2+ A_Three・ Q^-3
[0165]
[30]
B (q) = b₁・ Q^-1+ B₂・ Q^-2+ B_Three・ Q^-3
It can be expressed as. Therefore, the parameter vector θ and the data vector ψ (k) can be expressed as follows.
[0166]
[31]
θ = [a₁, A₂, A_Three, B₁, B₂, B_Three]^T
[0167]
[Expression 32]
ψ (k) = [− y (k−1), −y (k−2), −y (k−3), u (k−1), u (k−2), u (k−3) ]^T
Assuming that the total number of samplings N when the engine speed is 1200 rpm is N = 128 (1280 ms), Equations 24 to 26 are
[0168]
[Expression 33]

[0169]
[Expression 34]

[0170]
[Expression 35]

It can be expressed as.
[0171]
2.5 Input signals required for plant model identification
In order to identify the system, the input signal needs to excite all modes of the object. That is, the input signal needs to include a large number of frequency components. In system identification, whiteness input is ideally ideal, but in practice a pseudo-white binary signal (M series) is used. However, in the case of the engine wall flow response, the effective frequency band is very low (the response is slow), and almost no response waveform can be obtained even if an input such as an M-sequence is added. Therefore, the system is identified based on the waveform (see FIG. 12) obtained by giving the step input. Since the Laplace transform of the step input is 1 / s, the frequency gain decreases in inverse proportion to the frequency. Therefore, it is necessary to determine an effective frequency range from the power spectrum.
[0172]
2.6 Experimental results
Since the transfer function G (q, θ) of the system is determined by using the parameter θ thus determined, a Bode diagram in which the identification result and the actual data are superimposed is shown in FIG. The cut-off frequency tends to be higher). According to the experimental results, two gasolines with different fuel properties are separated by ± 3σ in the low load range when the swirl control valve provided at the intake port is open, the engine speed is around 1200 rpm, the cooling water temperature is around 40 ° C, and the low load range. I was able to.
[0173]
This concludes the description of the itemization.
[0174]
Next, the control content executed by the ECM 2 will be described according to a flowchart.
[0175]
FIG. 14 is for estimating the fuel property, and is executed at regular intervals (every 10 ms). Here, FIG. 14 is configured as the main routine, and FIGS. 15 and 16 are configured as the subroutine of FIG. 14. Therefore, in the following, the subroutine will be described when a step of the subroutine occurs during the description of the main routine.
[0176]
In FIG. 14, in step 1, the fuel property determined flag is viewed. When the fuel property has not been determined yet, the process proceeds to step 2 and subsequent steps.
[0177]
Steps 2 to 6 are parts for sampling the exhaust air-fuel ratio (output data). In step 2, the air-fuel ratio detected by the A / F sensor 3 is read, and in step 3, the read number (sampling number) S1 of this air-fuel ratio is compared with the total sampling number N (for example, 128). When S1 ≦ N, the routine proceeds to step 4 where the air-fuel ratio is buffered and the current processing is terminated. Steps 2 and 4 are repeated before S1> N.
[0178]
The process proceeds from step 3 to step 5 when S1> N. At this time, N pieces of output data are stored in the buffer. For example, the current value is y (1), the previous value is y (2), the previous value is y (3), ..., and the N-1 previous value is y (N). In this way, a total of N pieces of output data are stored.
[0179]
In steps 5 and 6, the output data N times before is discarded from the buffer, and the air / fuel ratio read this time is buffered. That is, the current value is stored in y (1). Needless to say, the past output data is shifted to the old side and stored once.
[0180]
Although not shown, the actual injection pulse width CTIn (input data) at the time of step response is also set to u (1), the previous value is u (2), the previous value is u (3), .., a total of N input data is stored in such a way that the value N-1 times before is u (N), and these input data and the above output data take into account the delay time described above Are associated with each other.
[0181]
Step 7 is a part for determining whether or not the estimation of the fuel property is permitted. Specific contents for this are shown in FIGS. The fuel property estimation permission determination is performed by checking the contents of steps 121 to 135 in FIGS. 40 and 41 one by one. When all of the items are satisfied, the fuel property estimation is permitted. When it is contrary, estimation of fuel properties is prohibited. That is,
A) The delay period DELAY1 # has elapsed since purge is prohibited and purge is prohibited (steps 121 and 122).
B) The delay period DELAY2 # has elapsed since the brake switch is turned off and the brake switch is turned off (steps 123 and 124).
C) The delay period DELAY3 # has elapsed since the cylinder distribution stable range and the cylinder distribution stable range have been reached (steps 125 and 126).
D) The delay period DELA Y4 # has elapsed since the misfire determination has not been made and the misfire determination has been canceled (steps 127 and 128).
E) While EGR (exhaust gas recirculation) is prohibited and the delay period DELAY5 # has elapsed since EGR was prohibited (steps 129 and 130),
F) The delay period DELAY6 # has elapsed since the swirl control valve was switched to the closed or open state (step 131).
G) The delay period DELAY7 # has elapsed since the lockup and the lockup (steps 132 and 133).
H) The delay period DELA Y8 # has elapsed since the fuel cut was not being performed and the fuel cut was recovered (steps 134 and 135).
In some cases, estimation of fuel properties is permitted in step 136 (estimation permission flag = 1). Otherwise, the process proceeds to step 137 and estimation of fuel properties is prohibited (estimation permission flag = 0).
[0182]
The above conditions A) to H) are simply listed in consideration of the presence of engines and vehicles of various specifications. Therefore, there are unnecessary items depending on the type of engine or vehicle. For example, when the vehicle has a manual specification, the above G) is not necessary. It can be configured simply by any one of the conditions.
[0183]
Here, a) during purge, b) when brake switch is ON, c) cylinder distribution unstable region, d) when misfire is judged, e) during EGR, f) immediately after switching of swirl control valve, and g) during non-lock-up H) The fuel property estimation is prohibited in each case during the fuel cut because the exhaust air-fuel ratio fluctuates due to factors other than the fuel property in these cases. This is because sampling results in inaccurate data, and estimation of fuel properties based on the inaccurate data reduces estimation accuracy.
[0184]
Hereinafter, the influence on the exhaust air-fuel ratio will be described in detail for each of the cases a) to g).
[0185]
a) The fuel vapor that evaporates in the fuel tank is guided to the canister and adsorbed on the activated carbon in the canister, and when the predetermined operating condition (purge ON condition) is reached, the purge valve is opened and the suction developed downstream of the throttle valve An engine equipped with a so-called evaporative fuel processing device that uses negative pressure and fresh air from an air introduction path provided in a canister to release fuel vapor adsorbed on activated carbon and introduce it into the intake pipe. is there. In this engine, if the engine is left for a considerable period of time before operation, the exhaust air / fuel ratio is less during purge for the first time (when the purge valve is opened) than when the purge is prohibited (when the purge valve is fully closed). Becomes richer.
[0186]
b) When the brake pedal is not depressed to assist braking ability, negative pressure developed downstream of the throttle valve is introduced into both chambers defined by the power piston in the power cylinder, and the brake pedal is depressed By switching the valve, the atmosphere is switched to only one chamber in the power cylinder and a pressure difference (difference between negative pressure and atmospheric pressure) is generated in the two chambers. There is a so-called hydro-back in which the hydraulic piston attached to the end of the push rod of the piston is moved to increase the hydraulic pressure from the master cylinder and send it to each wheel cylinder. The principle of boosting is exactly the same as that of the hydro back, and there is a master back that boosts the force pushing the piston of the master cylinder in front of the master cylinder. These are brake boosters that use negative pressure developed downstream of the throttle valve. In a vehicle equipped with this brake booster, when the brake pedal is depressed, the suction negative pressure fluctuates due to the operation of the brake booster. It becomes leaner than when the brake booster is inactive. In this case, whether or not the brake booster has been activated can be determined by looking at the brake switch. That is, when the brake switch is ON, the brake booster can be regarded as operating, and when the brake switch is OFF, the brake booster can be regarded as non-operating.
[0187]
  c) There is an engine in which a cylinder distribution unstable region (a region where the air-fuel ratio becomes unstable due to the influence of cylinder distribution) is determined in advance using the engine load and the rotational speed as parameters. In this engine, when the cylinder distribution unstable region is reached, the exhaust air-fuel ratio becomes leaner or richer than the cylinder distribution stable region.Here, “cylinder distribution” is a reduction in fuel distribution between cylinders.
[0188]
d) In an engine in which misfire determination is performed for use in diagnosis, the exhaust air-fuel ratio becomes leaner or richer than in non-misfire at the time of misfire determination (since misfire includes rich misfire and lean misfire).
[0189]
e) Some engines perform EGR to reduce NOx emissions. Since the EGR gas contains unburned components and inert gas, the exhaust air-fuel ratio becomes unstable during EGR, and the air-fuel ratio becomes leaner or richer than when EGR is prohibited.
[0190]
f) Some engines have a swirl control valve in the intake port to improve combustion at low loads. In this engine, when the swirl control valve is closed, the wall flow fuel amount changes (the intake flow velocity increases and the wall flow fuel amount decreases), which affects the exhaust air-fuel ratio.
[0191]
g) There is a vehicle including an automatic transmission with a so-called lockup mechanism in which an input shaft and an output shaft of a torque converter are directly connected. In this vehicle, the engine rotation speeds up faster when the lockup is not performed, and the rotation falls faster. In other words, the exhaust air-fuel ratio tends to become unstable during non-lock-up, and the exhaust air-fuel ratio becomes leaner or richer than during lock-up.
[0192]
h) There is an engine that performs so-called fuel cut that stops fuel supply when decelerating to save fuel. In this engine, the wall flow fuel amount changes during the fuel cut or immediately after the recovery from the fuel cut, which affects the exhaust air-fuel ratio.
[0193]
Next, the condition that the delay period (eg, time) has passed in steps 122, 124, 126, 128, 130, 131, 133, and 135 is that the brake switch is turned off immediately after the purge is prohibited. Immediately after the engine has shifted to the cylinder distribution stability range, immediately after the misfire determination is canceled, immediately after EGR is prohibited, immediately after the swirl control valve is switched, immediately after the lockup, and immediately after the fuel cut recovery Since the exhaust air-fuel ratio is not stable, the estimation of the fuel property is also prohibited during this period. In addition, what is necessary is just to determine an optimal value for each delay period by matching.
[0194]
Whether purge is prohibited or not is determined by the output signal to the purge valve, whether or not EGR is prohibited by the output signal to the EGR valve, and the operation state of the swirl control valve is determined by the output signal to the swirl control valve. Whether the lockup is in progress depends on the output signal to the solenoid for connecting / disconnecting the lockup clutch, and whether the cylinder distribution is stable is whether the operating point determined by the engine load and speed is in the cylinder distribution unstable Thus, it can be determined from the misfire determination flow whether the misfire has been determined, and from the fuel injection control flow, whether the fuel cut is being performed or whether the fuel cut has been recovered.
[0195]
As described above, even when the exhaust air-fuel ratio fluctuates due to factors other than the fuel property, sampling the exhaust air-fuel ratio as output data results in inaccurate data, and the fuel property is estimated based on this inaccurate data. However, in this embodiment, by prohibiting data sampling (thus estimating fuel properties) in this case, it is possible to prevent a decrease in estimation accuracy.
[0196]
When the determination of permission to estimate the fuel property is completed in this manner, the process returns to FIG. When the estimation permission determination flag = 0 (estimation prohibition condition), the process proceeds to steps 9 and 10, and 0 is entered in the number of exhaust air / fuel ratio readings (sampling number) s1, and all exhaust air / fuel ratio data (not shown) Delete the actual injection pulse width data).
[0197]
In steps 9 and 10, the sampling number is initialized to 0 and all the exhaust air-fuel ratio data is erased for the following reason. In order to analyze the response waveform of the exhaust air-fuel ratio (described later in step 12), a series of data from the beginning to the end of the transition is required. However, the exhaust air-fuel ratio fluctuates due to factors other than fuel properties during the transition. Even in this case, if the exhaust air / fuel ratio is sampled as output data, inaccurate data will be mixed and the response waveform of the exhaust air / fuel ratio cannot be analyzed accurately. It is.
[0198]
On the other hand, when the estimation permission determination flag = 1 (estimation permission condition), the process proceeds from step 8 to steps 11 and 12, and the exhaust air empty when the actual injection pulse width changes step by step using the above-mentioned N pieces of input / output data. The response waveform of the fuel ratio is analyzed, and the fuel property of the used fuel is estimated from the analysis result.
[0199]
Here, “analysis of the response waveform of the exhaust air / fuel ratio” means that, according to the above expression, the prediction error between the parameter θ of the ARX model (plant model) and the reference model is minimized based on the input / output data. To identify the ARX model. Therefore, the identification of the ARX model will be described with reference to the subroutine of FIG. 15, and the estimation of fuel properties will be described with reference to the subroutine of FIG.
[0200]
First, in FIG. 15, in step 21, input / output data in the buffer (u (1) to u (128) for input, −y (1) to −y (128) for output) is used to calculate data using Equation 32. A vector ψ (k) is created.
[0201]
In step 22, R (N) is calculated from the data vector ψ (k) using the above equation 33, and in step 23, the above equation 34 is calculated from the output data y (k) and this data vector ψ (k). To calculate f (N), and from these R (N) and f (N), in step 24, the model parameter θ is calculated using the above equation (28).
[0202]
Next, moving to FIG. 16, the transfer function G (q, θ) of the discrete-time LTI system is calculated from the model parameter θ thus obtained in step 31 (from the above equations 29 and 30). Are used to create A (q) and B (q), and G (q, θ) (= B (q) / A (q)) is calculated from the two.
[0203]
From this system transfer function G (q, θ), in step 32, the cutoff frequency fc of the ARX model._RealIs calculated. In step 33, this cutoff frequency fc_RealAnd the cut-off frequency fc of the reference model_RefCompare
[0204]
Here, since heavy gasoline is used as the reference fuel, if light gasoline is used, fc_Real> Fc_RefAnd fc when heavy gasoline is used_Real≤fc_RefIt becomes. Therefore, fc_Real> Fc_Ref(When light gasoline is used), the routine proceeds to step 34, where the fuel property switching flag = 1 is set._Real≤fc_Ref(When heavy gasoline is used), the routine proceeds from step 33 to step 35, where the fuel property switching flag = 0.
[0205]
When the determination as to which fuel is being used is completed in this way, the process proceeds to step 13 in FIG. 14, where the value of the fuel property switching flag (the fuel property determination result) is stored in the EEPROM, and then in step 14 The fuel property determined flag = 1. Due to the processing of the fuel property determination flag = 1, it is not possible to proceed to step 2 and subsequent steps in FIG. 14 after the next time (the number of times of determination of the fuel property is only one).
[0206]
When the fuel property can be determined in this way, various correction amounts of the fuel injection amount and the fuel injection amount at start-up can be given according to the difference in the fuel property. This will be specifically described in the case of KAS.
[0207]
FIG. 17 is for calculating the post-startup increase correction coefficient KAS, and is executed at regular time intervals (for example, every 10 ms).
[0208]
In step 41, the fuel property switching flag stored in the EEPROM is read. In step 42, when the starter switch is viewed and it is ON, the process proceeds to step 43, and the coolant temperature TW and the rotational speed Ne are read. Of these, the post-startup increase water temperature correction value TKAS and the second post-startup increase correction coefficient are obtained by searching the tables having the contents shown in FIGS. 18 and 19 in steps 44 and 45 from the values of the cooling water temperature TW and the fuel property switching flag. In step 46, KASS is calculated from the rotation speed Ne and the value of the fuel property switching flag, and a post-start-up increasing rotation correction value TNKAS is calculated in step 46, and these values are used in step 47.
[0209]
[Expression 36]
KAS = TKAS x TNKAS + KASS
The post-startup increase correction coefficient KAS is calculated by the following formula.
[0210]
In step 48, in order to prepare for the processing after the starter switch is turned OFF, the value of TKAS is set to TKAS._n-1The KASS value to KASS_n-1To end the current process. TKAS_n-1, KASS_n-1Is a memory for holding the previous value.
[0211]
Eventually, when the starter switch is turned off (startup complete explosion), the operation proceeds from step 42 to the attenuation operation after step 49.
[0212]
In step 49, a post-start increase / decrease time ratio TMKAS is calculated by searching a table having the contents shown in FIG. 21 from the value of the fuel property switching flag and the post-start time t. In step 50, the previous value is decreased by this value. This value is the current TKAS (= TKAS_n-1-TMKAS). Immediately after the starter switch is turned off, TKAS> 0, so the process proceeds to step 53 as it is.
[0213]
Steps 53 to 56 are the same as steps 49 to 52. In step 53, the second post-startup increase / decrease time ratio TMKASS is calculated by searching a table having the contents shown in FIG. 22 from the value of the fuel property determination flag and the post-startup time t. In step 54, the previous value is decreased by this value. This value is the current KASS (= KASS_n-1-TMKASS). Also at this time, since KASS> 0, the process proceeds to step 46 as it is, and the processing after step 36 is executed.
[0214]
Since the steps 49, 50, 53, and 54 are repeated from the next time onward, TKAS and KASS eventually become 0 or less. At this time, the process proceeds to step 52 and step 56 to limit TKAS and KASS to 0.
[0215]
As a result, both TKAS and KASS are initially set to the value when the starter switch is OFF, and are attenuated at a constant rate to 0 after the starter switch is turned OFF (however, when TNKAS is constant). However, the initial value of TKAS is larger than the initial value of KASS, and the decrease time ratio of TKAS is larger than the decrease time ratio of KASS. Therefore, KAS, which is a value obtained by adding TKAS and KASS, first decreases with a steep slope after turning off the starter switch, with the initial value being the sum of the TKAS value and KASS value when the starter switch is turned off, and TKAS becomes zero. From this timing, it changes to a gentle slope and decreases.
[0216]
In this case, the initial values of TKAS and KASS (table values in FIGS. 18 and 19) are smaller when light gasoline is used than when heavy gasoline is used, and the respective reduction time ratios of TKAS and KASS (FIG. 21 and the table values in FIG. 22) are increased, so that KAS when light gasoline is used is smaller than KAS when heavy gasoline is used (see FIG. 23). In other words, when the fuel property is not judged, the air-fuel ratio is enriched by using a table value matched to heavy gasoline even when light gasoline is used. When it is determined that gasoline is being used, the KAS for light gasoline is calculated when calculating KAS at the next start, so that the air-fuel ratio will not be biased to the rich side even when light gasoline is used. is there.
[0217]
The flowchart of FIG. 24 is a second embodiment and corresponds to FIG. 16 of the first embodiment. The same steps as those in FIG. 16 are denoted by the same step numbers.
[0218]
In contrast to the first embodiment in which heavy gasoline is used as the reference fuel, the second embodiment uses an almost intermediate fuel that is neither bad nor bad among commercially available fuels as a reference fuel. The fuel that is more volatile than the reference fuel is set as light gasoline, and conversely, the fuel that is less volatile than the reference fuel is set as heavy gasoline, and the cutoff frequency of the plant model and the cutoff frequency of the reference model (that is, The difference between the cutoff frequency and the reference fuel is calculated, and the difference between the frequency difference and the allowable range is compared to determine the fuel properties of the fuel being used. Even if there is a variation, fuel property estimation can be performed stably.
[0219]
In FIG. 24, the part different from FIG.
[0220]
[Expression 37]
Δfc = fc_Real-Fc_Ref
The cut-off frequency difference Δfc with respect to the reference fuel is calculated by the following formula, and the absolute value of this frequency difference Δfc and a predetermined value a (> 0) that defines an allowable range, or Δfc and a are compared in steps 62 and 63. If | Δfc | ≦ a (that is, the reference fuel is used), the routine proceeds from step 62 to step 64 where the fuel property switching 2 flag = 0, and | Δfc |> a and Δfc> a (that is, light gasoline is Is used), the process proceeds from step 63 to step 65 to set the fuel property switching 2 flag = 1. Otherwise (that is, heavy gasoline is used), the process proceeds from step 63 to step 66. The fuel property switching 2 flag = 2.
[0221]
Thus, in 2nd Embodiment, it was determined whether the fuel currently used is a reference fuel, light gasoline, or heavy gasoline.
[0222]
However, when the fuel property determination value becomes three values as in the second embodiment, it is necessary to prepare three types of table values corresponding to FIGS. 18 to 22 when calculating the post-startup increase correction coefficient KAS. There is.
[0223]
Next, the flowcharts of FIGS. 25, 26, and 28 are the third embodiment, and correspond to FIGS. 14, 16, and 17 of the first embodiment, respectively. In FIG. 25, the same step numbers are assigned to the same portions as FIG. 14, the same portions as FIG. 16 in FIG. 26, and the same portions as FIG.
[0224]
Whereas in the above-described two embodiments, the fuel property determination value (that is, the value of the fuel property switching flag or the fuel property switching 2 flag) is binary or ternary, the third embodiment is a continuous value. The estimated fuel property value is calculated and stored in the EEPROM (steps 71 and 72 in FIG. 25), and the post-startup increase correction coefficient KAS is calculated using the estimated fuel property value at the next start. Is.
[0225]
The calculation of the estimated fuel property value will be described in detail with reference to FIG. 26. In steps 31 and 32, the cutoff frequency of the plant model is calculated in the same manner as in the first embodiment, and in FIG. The fuel property estimation value is calculated by searching a table having the contents of. Since the relationship between the cut-off frequency of the plant model and the estimated fuel property value is as shown in FIG. 27, the fuel property of the fuel used can be estimated from the cut-off frequency of the plant model if the same characteristic is determined in advance by matching. is there.
[0226]
Next, in FIG. 28, the difference from FIG. 17 will be mainly described. In step 91, the fuel property estimation value FC is read. When the starter switch is turned on, the value FC, the cooling water temperature TW, and the rotational speed Ne are used to determine the step 92, 93, 94, a map containing the contents of FIGS. 29, 30 and 31 is searched to obtain the post-startup increase water temperature correction value TKAS, the second post-startup increase correction coefficient KASS, the post-startup increase rotation correction value TNKAS, and When the starter switch is turned OFF, the fuel property estimated value FC and the coolant temperature TW are searched from the maps having the contents shown in FIGS. 32 and 33 in steps 95 and 96, so that the increase / decrease time ratio TMKAS after the start and the increase / decrease after the second start. Each time ratio TMKASS is calculated.
[0227]
Here, as shown in FIG. 29 and FIG. 30, TKAS and KASS are values that increase as the cooling water temperature TW decreases and the fuel properties become heavier when the TW is the same, TMKAS TMKASS is a value that increases as the cooling water temperature TW increases for the same FC as shown in FIGS. 32 and 33, and as the fuel property becomes lighter when the TW is the same.
[0228]
Needless to say, if the fuel property estimated value and the TW are the same, TKAS is larger than KASS and TMKAS is larger than TMKASS.
[0229]
According to the third embodiment, since the data (map value) used for the calculation of the post-startup increase correction coefficient KAS is assigned according to the fuel property estimated value FC as the continuous value, it is more than the previous two embodiments. Thus, the calculation accuracy of the post-startup increase correction coefficient KAS is improved.
[0230]
The flowchart of FIG. 34 is the fourth embodiment, which replaces FIG. 28 of the third embodiment. The same steps as those in FIG. 28 are denoted by the same step numbers.
[0231]
Now, if the data used to calculate KAS is given as map values as shown in FIGS. 29 to 33, the number of matching steps becomes enormous. Therefore, in the fourth embodiment, a fuel property correction value KFC corresponding to the fuel property estimation value FC is introduced, and the data (table value) matched with the heaviest gasoline is corrected by this correction value KFC. By calculating the post-startup increase correction coefficient KAS based on the obtained data, the number of matching man-hours is reduced.
[0232]
Specifically, steps 101 and 102 to 115 are different from the case of FIG. First, in step 101, a fuel property correction value KFC is calculated by searching a table having the contents shown in FIG. 35 from the fuel property estimation value FC. As shown in FIG. 35, KFC is a value that becomes smaller as the fuel property becomes lighter with 1.0 being the maximum when the fuel is the heaviest gasoline (fuel property is the most heavy).
[0233]
In steps 102 and 103, a table containing the contents of FIG. 36 and FIG. 37 is searched from the coolant temperature TW to calculate TKAS and TMKAS (both are values matched to the heaviest gasoline). In step 104 using the above KFC,
[0234]
[Formula 38]
TKASF = TKAS × KFC
TMKASF = TMKAS × KFC
The post-startup increase water temperature correction value TKASF corresponding to the fuel property and the post-startup increase decrease time ratio TMKASF corresponding to the fuel property are calculated by the following equation. In Steps 105, 106, and 107, as in Steps 102, 103, and 104, by searching the table containing the contents of FIGS. 38 and 39 from the cooling water temperature TW, KASS and TMKASS Is a matching value)
[0235]
[39]
KASSF = KASS × KFC
TMKASSF = TMKASS × KFC
The second post-startup increase correction coefficient KASSF corresponding to the fuel property and the second post-startup increase decrease time ratio TMKASF corresponding to the fuel property are calculated by the following equation. And using these values, it is the same formula as the above-mentioned formula 36,
[0236]
[Formula 40]
KAS = TKASF × TNKAS + KASSF
The post-startup increase correction coefficient KAS is calculated by the following equation (step 108).
[0237]
In step 109, the TKASF value is set to TKASF in order to prepare for the processing after the starter switch is turned off._n-1The value of KASSF to KASSF_n-1To end the current process. Steps 110 to 115 are parts for performing a damping operation on TKASF and KASSF in the same manner as steps 49 to 56 in FIG. 17 after the starter switch is turned off.
[0238]
For example, when gasoline having a lighter fuel property than the heaviest gasoline is used, the KFC becomes a value smaller than 1.0. Therefore, a KAS smaller than the KAS for the heaviest gasoline is calculated, and as a result, as in the case of FIG. 28, the optimum post-start-up increase is also obtained for the lighter fuel property than the heaviest gasoline. A correction factor is given. When using the heaviest gasoline, KFC = 1.0, TKASF = TKAS, TMKASF = TMKAS, KASSF = KASS, and TMKASF = TMKASS, which are the same as the conventional apparatus.
[0239]
In this case, when obtaining the data used for the calculation of KAS, it is only necessary to match the characteristics shown in FIG. 36 to FIG. 39 with the heaviest gasoline, so according to the fourth embodiment, the third embodiment. The matching man-hour can be reduced as compared with the case of (1).
[0240]
In each of the first, third, and fourth embodiments described above, (A) the fuel property switching flag is used for the post-startup increase correction coefficient KAS as the injection amount correction amount, and (B) the fuel property estimated value FC. (C) Although the case where the fuel property correction value KFC is used has been described, the present invention is not limited to this. For example, the following three cases (A) to (C) can be applied to the following injection amount correction amounts (1) to (4) and fuel injection amounts (5) and (6).
[0241]
(1) Low frequency component (wall flow fuel).
[0242]
(2) High frequency component (wall flow fuel).
[0243]
(3) Water temperature increase correction amount.
[0244]
(4) Unburned amount increase correction amount.
[0245]
(5) Fuel injection amount at start-up.
[0246]
(6) Acceleration interruption injection amount.
[0247]
Here, (1) and (2) are described in Japanese Patent Application No. 8-173802, (3) and (4) are described in Japanese Patent Application No. 8-173803, and (5) is disclosed in JP-A-7-63082. (6) is known from Japanese Patent Application Laid-Open No. 64-3245, and will not be described in detail.
[0248]
In the embodiment, the response waveform of the exhaust air / fuel ratio with respect to the fuel injection amount at the time of transient is sampled, and based on these transient data, the parameters of the plant model built in advance on the ECM are changed to the reference model that is the plant model for the reference fuel. However, the present invention is not limited to this, and the fuel supply amount can be used instead of the fuel injection amount. . Further, in addition to adjusting so that the prediction error is minimized, it may be adjusted so as to reduce the prediction error.
[0249]
Moreover, the estimation method of the fuel property of the fuel used is not limited to that of the embodiment.
[Brief description of the drawings]
FIG. 1 is a control system diagram of engine control.
FIG. 2 is a control system diagram related to estimation of fuel properties.
FIG. 3 is a block diagram of an engine plant model.
FIG. 4 is a model diagram of fuel behavior.
FIG. 5 is a parallel path block diagram of fuel behavior.
FIG. 6 is an exhaust model diagram.
FIG. 7 is a waveform diagram showing dead time between input and output.
FIG. 8 is a table in which dead times are classified.
FIG. 9 is a general block diagram of an LTI system.
FIG. 10 is a characteristic diagram of an evaluation function (evaluation standard).
FIG. 11 is a flowchart showing a method for identifying an ARX model.
FIG. 12 is a waveform diagram showing an input signal necessary for model identification and its response.
FIG. 13 is a Bode diagram showing the identification result and actual data superimposed on each other.
FIG. 14 is a flowchart for explaining estimation of fuel properties.
FIG. 15 is a flowchart for explaining identification of an ARX model.
FIG. 16 is a flowchart for explaining fuel property switching determination;
FIG. 17 is a flowchart for explaining calculation of a post-startup increase correction coefficient KAS.
FIG. 18 is a characteristic diagram of a post-startup increased water temperature correction value (initial value).
FIG. 19 is a characteristic diagram of an increase correction coefficient (initial value) after the second start.
FIG. 20 is a characteristic diagram of an increased rotation correction value after startup.
FIG. 21 is a characteristic diagram of an increase / decrease time ratio after start.
FIG. 22 is a characteristic diagram of the increase / decrease time ratio after the second start.
FIG. 23 is a waveform diagram showing a time-series image of a post-startup increase correction coefficient KAS.
FIG. 24 is a flowchart for explaining fuel property switching determination according to the second embodiment;
FIG. 25 is a flowchart for explaining fuel property estimation according to the third embodiment;
FIG. 26 is a flowchart for explaining calculation of a fuel property estimated value according to the third embodiment.
FIG. 27 is a characteristic diagram of a fuel property estimation value with respect to a cutoff frequency.
FIG. 28 is a flowchart for explaining calculation of a post-startup increase correction coefficient KAS according to the third embodiment.
FIG. 29 is a characteristic diagram of a post-startup increased water temperature correction value (initial value) according to the third embodiment.
FIG. 30 is a characteristic diagram of a second post-startup increase correction coefficient (initial value) of the third embodiment.
FIG. 31 is a characteristic diagram of a post-startup increased rotation correction value of the third embodiment.
FIG. 32 is a characteristic diagram of an increase / decrease time ratio after start of the third embodiment.
FIG. 33 is a characteristic diagram of an increase / decrease time ratio after the second start according to the third embodiment.
FIG. 34 is a flowchart for explaining calculation of a post-startup increase correction coefficient KAS according to the third embodiment.
FIG. 35 is a characteristic diagram of a fuel property correction value according to the third embodiment.
FIG. 36 is a characteristic diagram of a post-startup increased water temperature correction value (initial value) according to the third embodiment.
FIG. 37 is a characteristic diagram of an increase / decrease time ratio after start of the third embodiment.
FIG. 38 is a characteristic diagram of an increase correction coefficient (initial value) after the second start according to the third embodiment.
FIG. 39 is a characteristic diagram of the increase / decrease time ratio after the second start according to the third embodiment.
FIG. 40 is a flowchart for explaining fuel property estimation permission determination;
FIG. 41 is a flowchart for explaining fuel property estimation permission determination;
FIG. 42 is a diagram corresponding to claims of the first invention.
FIG. 43 is a diagram corresponding to claims of the second invention.
44 is a view corresponding to claims of the third invention. FIG.
FIG. 459FIG.
FIG. 4610FIG.
FIG. 4711FIG.
[Explanation of symbols]
2 ECM
3 A / F sensor
7 Fuel injection valve
14 EEPROM
21 Plant Identification Department
22 Fuel property estimation part
23 Triggering function
24 controller
31 Plant model
37 normative model
38 Comparison means

Claims (16)

Means for calculating the fuel supply amount according to the engine operating conditions;
Means for supplying this amount of fuel to the engine;
Means for detecting the exhaust air-fuel ratio of the engine;
Means for sampling the fuel supply amount at the time of transition, sampling the exhaust air / fuel ratio response waveform data with respect to the fuel supply amount with the currently used fuel, using the exhaust air / fuel ratio as an output;
Based on these input / output data, means for identifying the plant model for the fuel used by adjusting the parameters of the plant model constructed in advance so that the prediction error with the reference model is small;
Means for calculating a cutoff frequency of the identified plant model;
Means for comparing the cut-off frequency of the plant model and the cut-off frequency of the reference model to estimate the fuel property of the fuel used;
Means for determining whether the region in which the exhaust air-fuel ratio fluctuates due to factors other than the fuel property is any one of the following states 1 to 15 ;
State 1: The fuel vapor that evaporates in the fuel tank is guided to the canister and adsorbed on the activated carbon in the canister, the purge valve is opened under the purge ON condition, the suction negative pressure developed downstream of the throttle valve , and the canister Purging when equipped with a device that uses fresh air from the air introduction path to separate the fuel vapor adsorbed on the activated carbon and introduce it into the intake pipe
State 2: The fuel vapor that evaporates in the fuel tank is guided to the canister and adsorbed to the activated carbon in the canister, the purge valve is opened when the predetermined operating condition is reached, the suction negative pressure developed downstream of the throttle valve , and the canister When equipped with a device that uses fresh air from the installed air introduction path to release the fuel vapor adsorbed on the activated carbon and introduces it into the intake pipe , the purge period is prohibited and the delay period is longer than the purge is prohibited. It has not passed
Condition 3: if with a brake booster that utilizes negative pressure to develop in the downstream throttle valve, an ON time of the brake switch
Condition 4: when equipped with a brake booster that utilizes negative pressure to develop in the downstream throttle valve, OFF time and a brake switch of the brake switch is in a state that has not elapsed Delay period more turned OFF
Condition 5: when the cylinders distribution unstable region has a predetermined number of rotation and the load of the engine as parameters, is the cylinder distribution unstable region
Condition 6: When the cylinders distribution unstable region has a predetermined number of rotation and the load of the engine as a parameter, has not elapsed more de Irei period turned it and cylinder dispensing stable region in the cylinder partitioned stable range condition Is
State 7: When a misfire determination function is provided, it is a misfire determination time.
State 8: When the misfire determination function is provided, the delay period has not elapsed since the misfire determination is canceled and the misfire determination is canceled.
State 9: When EGR device is provided, EGR is in progress
Condition 10: a case of providing the EGR device is in a state of Delay period more banned and EGR in EGR prohibition has not elapsed
Condition 11: a case of providing the swirl control valve is in a state that has not passed more delay periods to the swirl control valves in a closed state or an open state
State 12: When an automatic transmission with a lock-up mechanism is in the non-lockup
State 13: In a state where an automatic transmission with a lock-up mechanism is provided, the delay period has not elapsed since the lock-up and the lock-up.
State 14: When a fuel cut function is provided, the fuel is being cut
Condition 15: a case of providing a fuel cut function, area delay period from and fuel Kattorika bar not in a fuel cut is in the state not elapsed exhaust air-fuel ratio by a factor other than the fuel property from the result of this determination is to change the A fuel property detection device comprising: means for prohibiting sampling of the input / output data when in any one of states 1 to 15 . Means for calculating the fuel supply amount according to the engine operating conditions;
Means for supplying this amount of fuel to the engine;
Means for detecting the exhaust air-fuel ratio of the engine;
Means for sampling the fuel supply amount at the time of transition, sampling the exhaust air / fuel ratio response waveform data with respect to the fuel supply amount with the currently used fuel, using the exhaust air / fuel ratio as an output;
Based on these input / output data, means for identifying the plant model for the fuel used by adjusting the parameters of the plant model constructed in advance so that the prediction error with the reference model is small;
Means for calculating a cutoff frequency of the identified plant model;
Means for comparing the difference between the cutoff frequency of the plant model and the cutoff frequency of the reference model and an allowable range to estimate the fuel property of the fuel used;
Means for determining whether the region in which the exhaust air-fuel ratio fluctuates due to factors other than the fuel property is any one of the following states 1 to 15 ;
State 1: The fuel vapor that evaporates in the fuel tank is guided to the canister and adsorbed on the activated carbon in the canister, the purge valve is opened under the purge ON condition, the suction negative pressure developed downstream of the throttle valve , and the canister Purging when equipped with a device that uses fresh air from the air introduction path to separate the fuel vapor adsorbed on the activated carbon and introduce it into the intake pipe
State 2: The fuel vapor that evaporates in the fuel tank is guided to the canister and adsorbed to the activated carbon in the canister, the purge valve is opened when the predetermined operating condition is reached, the suction negative pressure developed downstream of the throttle valve , and the canister When equipped with a device that uses fresh air from the installed air introduction path to release the fuel vapor adsorbed on the activated carbon and introduces it into the intake pipe , the purge period is prohibited and the delay period is longer than the purge is prohibited. It has not passed
Condition 3: if with a brake booster that utilizes negative pressure to develop in the downstream throttle valve, an ON time of the brake switch
Condition 4: when equipped with a brake booster that utilizes negative pressure to develop in the downstream throttle valve, OFF time and a brake switch of the brake switch is in a state that has not elapsed Delay period more turned OFF
Condition 5: when the cylinders distribution unstable region has a predetermined number of rotation and the load of the engine as parameters, is the cylinder distribution unstable region
Condition 6: When the cylinders distribution unstable region has a predetermined number of rotation and the load of the engine as a parameter, has not elapsed more de Irei period turned it and cylinder dispensing stable region in the cylinder partitioned stable range condition Is
State 7: When a misfire determination function is provided, it is a misfire determination time.
State 8: When the misfire determination function is provided, the delay period has not elapsed since the misfire determination is canceled and the misfire determination is canceled.
State 9: When EGR device is provided, EGR is in progress
Condition 10: a case of providing the EGR device is in a state of Delay period more banned and EGR in EGR prohibition has not elapsed
Condition 11: a case of providing the swirl control valve is in a state that has not passed more delay periods to the swirl control valves in a closed state or an open state
State 12: When an automatic transmission with a lock-up mechanism is in the non-lockup
State 13: In a state where an automatic transmission with a lock-up mechanism is provided, the delay period has not elapsed since the lock-up and the lock-up.
State 14: When a fuel cut function is provided, the fuel is being cut
Condition 15: a case of providing a fuel cut function, area delay period from and fuel Kattorika bar not in a fuel cut is in the state not elapsed exhaust air-fuel ratio by a factor other than the fuel property from the result of this determination is to change the A fuel property detection device comprising: means for prohibiting sampling of the input / output data when in any one of states 1 to 15 . Means for calculating the fuel supply amount according to the engine operating conditions;
Means for supplying this amount of fuel to the engine;
Means for detecting the exhaust air-fuel ratio of the engine;
Means for sampling the fuel supply amount at the time of transition, sampling the exhaust air / fuel ratio response waveform data with respect to the fuel supply amount with the currently used fuel, using the exhaust air / fuel ratio as an output;
Based on these input / output data, means for identifying the plant model for the fuel used by adjusting the parameters of the plant model constructed in advance so that the prediction error with the reference model is small;
Means for calculating a cutoff frequency of the identified plant model;
Means for presetting the property of the fuel property estimate with respect to the cutoff frequency;
Means for calculating a fuel property estimated value by retrieving this characteristic from the calculated cutoff frequency;
Means for determining whether the region in which the exhaust air-fuel ratio fluctuates due to factors other than the fuel property is any one of the following states 1 to 15 ;
State 1: The fuel vapor that evaporates in the fuel tank is guided to the canister and adsorbed on the activated carbon in the canister, the purge valve is opened under the purge ON condition, the suction negative pressure developed downstream of the throttle valve , and the canister Purging when equipped with a device that uses fresh air from the air introduction path to separate the fuel vapor adsorbed on the activated carbon and introduce it into the intake pipe
State 2: The fuel vapor that evaporates in the fuel tank is guided to the canister and adsorbed to the activated carbon in the canister, the purge valve is opened when the predetermined operating condition is reached, the suction negative pressure developed downstream of the throttle valve , and the canister When equipped with a device that uses fresh air from the installed air introduction path to release the fuel vapor adsorbed on the activated carbon and introduces it into the intake pipe , the purge period is prohibited and the delay period is longer than the purge is prohibited. It has not passed
Condition 3: if with a brake booster that utilizes negative pressure to develop in the downstream throttle valve, an ON time of the brake switch
Condition 4: when equipped with a brake booster that utilizes negative pressure to develop in the downstream throttle valve, OFF time and a brake switch of the brake switch is in a state that has not elapsed Delay period more turned OFF
Condition 5: when the cylinders distribution unstable region has a predetermined number of rotation and the load of the engine as parameters, is the cylinder distribution unstable region
Condition 6: When the cylinders distribution unstable region has a predetermined number of rotation and the load of the engine as a parameter, has not elapsed more de Irei period turned it and cylinder dispensing stable region in the cylinder partitioned stable range condition Is
State 7: When a misfire determination function is provided, it is a misfire determination time.
State 8: When the misfire determination function is provided, the delay period has not elapsed since the misfire determination is canceled and the misfire determination is canceled.
State 9: When EGR device is provided, EGR is in progress
Condition 10: a case of providing the EGR device is in a state of Delay period more banned and EGR in EGR prohibition has not elapsed
Condition 11: a case of providing the swirl control valve is in a state that has not passed more delay periods to the swirl control valves in a closed state or an open state
State 12: When an automatic transmission with a lock-up mechanism is in the non-lockup
State 13: In a state where an automatic transmission with a lock-up mechanism is provided, the delay period has not elapsed since the lock-up and the lock-up.
State 14: When a fuel cut function is provided, the fuel is being cut
Condition 15: a case of providing a fuel cut function, area delay period from and fuel Kattorika bar not in a fuel cut is in the state not elapsed exhaust air-fuel ratio by a factor other than the fuel property from the result of this determination is to change the A fuel property detection device comprising: means for prohibiting sampling of the input / output data when in any one of states 1 to 15 . The fuel property detection device according to claim 1 or 2 , wherein the estimation result of the fuel property is stored in a nonvolatile memory. The fuel property detection device according to claim 3 , wherein the estimated fuel property value is stored in a nonvolatile memory. The estimation of the fuel property is lighter than the reference fuel when the identified model model has a cutoff frequency higher than the cutoff frequency of the reference model when the reference model is matched with the reference fuel. The fuel property detection device according to claim 1 , wherein the estimation is estimation. The estimation of the fuel property is such that, when the reference model is matched with a reference fuel, a difference between the cut-off frequency of the identified plant model and the cut-off frequency of the reference model is outside an allowable range, and the plant model The fuel property detection device according to claim 2 , wherein when the cutoff frequency is higher than the cutoff frequency of the reference model, the fuel property is estimated to be lighter than the reference fuel. The adjustment according to any one of claims 1 , 2, 3, 5, 6 , and 7 , wherein adjusting the prediction error to be small is adjusting the prediction error to be a minimum. The fuel property detection apparatus as described. Means for supplying the engine with a fuel supply amount corresponding to the engine operating conditions;
Means for detecting the exhaust air-fuel ratio of the engine;
Means for sampling the fuel supply amount at the time of transition, sampling the exhaust air / fuel ratio response waveform data with respect to the fuel supply amount with the currently used fuel, using the exhaust air / fuel ratio as an output;
Based on these input / output data, means for identifying the plant model for the fuel used by adjusting the parameters of the plant model constructed in advance so that the prediction error with the reference model is small;
Means for calculating a cutoff frequency of the identified plant model;
Means for comparing the cut-off frequency of the plant model and the cut-off frequency of the reference model to estimate the fuel property of the fuel used;
Means for calculating the fuel supply jet based on the estimation result of the fuel property;
Means for determining whether the region where the exhaust air-fuel ratio fluctuates due to a factor other than the fuel property is any one of the following states 1 to 15 ;
State 1: The fuel vapor that evaporates in the fuel tank is guided to the canister and adsorbed on the activated carbon in the canister, the purge valve is opened under the purge ON condition, the suction negative pressure developed downstream of the throttle valve , and the canister Purging when equipped with a device that uses fresh air from the air introduction path to separate the fuel vapor adsorbed on the activated carbon and introduce it into the intake pipe
State 2: The fuel vapor that evaporates in the fuel tank is guided to the canister and adsorbed to the activated carbon in the canister, the purge valve is opened when the predetermined operating condition is reached, the suction negative pressure developed downstream of the throttle valve , and the canister When equipped with a device that uses fresh air from the installed air introduction path to release the fuel vapor adsorbed on the activated carbon and introduces it into the intake pipe , the purge period is prohibited and the delay period is longer than the purge is prohibited. It has not passed
Condition 3: if with a brake booster that utilizes negative pressure to develop in the downstream throttle valve, an ON time of the brake switch
Condition 4: when equipped with a brake booster that utilizes negative pressure to develop in the downstream throttle valve, OFF time and a brake switch of the brake switch is in a state that has not elapsed Delay period more turned OFF
Condition 5: when the cylinders distribution unstable region has a predetermined number of rotation and the load of the engine as parameters, is the cylinder distribution unstable region
Condition 6: When the cylinders distribution unstable region has a predetermined number of rotation and the load of the engine as a parameter, has not elapsed more de Irei period turned it and cylinder dispensing stable region in the cylinder partitioned stable range condition Is
State 7: When a misfire determination function is provided, it is a misfire determination time.
State 8: When the misfire determination function is provided, the delay period has not elapsed since the misfire determination is canceled and the misfire determination is canceled.
State 9: When EGR device is provided, EGR is in progress
Condition 10: a case of providing the EGR device is in a state of Delay period more banned and EGR in EGR prohibition has not elapsed
Condition 11: a case of providing the swirl control valve is in a state that has not passed more delay periods to the swirl control valves in a closed state or an open state
State 12: When an automatic transmission with a lock-up mechanism is in the non-lockup
State 13: In a state where an automatic transmission with a lock-up mechanism is provided, the delay period has not elapsed since the lock-up and the lock-up.
State 14: When a fuel cut function is provided, the fuel is being cut
Condition 15: a case of providing a fuel cut function, area delay period from and fuel Kattorika bar not in a fuel cut is in the state not elapsed exhaust air-fuel ratio by a factor other than the fuel property from the result of this determination is to change the A fuel supply control device for an engine, comprising: means for prohibiting sampling of the input / output data in any one of states 1 to 15 . Means for supplying the engine with a fuel supply amount corresponding to the engine operating conditions;
Means for detecting the exhaust air-fuel ratio of the engine;
Means for sampling the fuel supply amount at the time of transition, sampling the exhaust air / fuel ratio response waveform data with respect to the fuel supply amount with the currently used fuel, using the exhaust air / fuel ratio as an output;
Based on these input / output data, means for identifying the plant model for the fuel used by adjusting the parameters of the plant model constructed in advance so that the prediction error with the reference model is small;
Means for calculating a cutoff frequency of the identified plant model;
Means for comparing the difference between the cutoff frequency of the plant model and the cutoff frequency of the reference model and an allowable range to estimate the fuel property of the fuel used;
Means for calculating the fuel supply amount based on the estimation result of the fuel property;
Means for determining whether the region where the exhaust air-fuel ratio fluctuates due to a factor other than the fuel property is any one of the following states 1 to 15 ;
State 1: The fuel vapor that evaporates in the fuel tank is guided to the canister and adsorbed on the activated carbon in the canister, the purge valve is opened under the purge ON condition, the suction negative pressure developed downstream of the throttle valve , and the canister Purging when equipped with a device that uses fresh air from the air introduction path to separate the fuel vapor adsorbed on the activated carbon and introduce it into the intake pipe
State 2: The fuel vapor that evaporates in the fuel tank is guided to the canister and adsorbed to the activated carbon in the canister, the purge valve is opened when the predetermined operating condition is reached, the suction negative pressure developed downstream of the throttle valve , and the canister When equipped with a device that uses fresh air from the installed air introduction path to release the fuel vapor adsorbed on the activated carbon and introduces it into the intake pipe , the purge period is prohibited and the delay period is longer than the purge is prohibited. It has not passed
Condition 3: if with a brake booster that utilizes negative pressure to develop in the downstream throttle valve, an ON time of the brake switch
Condition 4: when equipped with a brake booster that utilizes negative pressure to develop in the downstream throttle valve, OFF time and a brake switch of the brake switch is in a state that has not elapsed Delay period more turned OFF
Condition 5: when the cylinders distribution unstable region has a predetermined number of rotation and the load of the engine as parameters, is the cylinder distribution unstable region
Condition 6: When the cylinders distribution unstable region has a predetermined number of rotation and the load of the engine as a parameter, has not elapsed more de Irei period turned it and cylinder dispensing stable region in the cylinder partitioned stable range condition Is
State 7: When a misfire determination function is provided, it is a misfire determination time.
State 8: When the misfire determination function is provided, the delay period has not elapsed since the misfire determination is canceled and the misfire determination is canceled.
State 9: When EGR device is provided, EGR is in progress
Condition 10: a case of providing the EGR device is in a state of Delay period more banned and EGR in EGR prohibition has not elapsed
Condition 11: a case of providing the swirl control valve is in a state that has not passed more delay periods to the swirl control valves in a closed state or an open state
State 12: When an automatic transmission with a lock-up mechanism is in the non-lockup
State 13: In a state where an automatic transmission with a lock-up mechanism is provided, the delay period has not elapsed since the lock-up and the lock-up.
State 14: When a fuel cut function is provided, the fuel is being cut
Condition 15: a case of providing a fuel cut function, area delay period from and fuel Kattorika bar not in a fuel cut is in the state not elapsed exhaust air-fuel ratio by a factor other than the fuel property from the result of this determination is to change the A fuel supply control device for an engine, comprising: means for prohibiting sampling of the input / output data in any one of states 1 to 15 . Means for supplying the engine with a fuel supply amount corresponding to the engine operating conditions;
Means for detecting the exhaust air-fuel ratio of the engine;
Means for sampling the fuel supply amount at the time of transition, sampling the exhaust air / fuel ratio response waveform data with respect to the fuel supply amount with the currently used fuel, using the exhaust air / fuel ratio as an output;
Based on these input / output data, means for identifying the plant model for the fuel used by adjusting the parameters of the plant model constructed in advance so that the prediction error with the reference model is small;
Means for calculating a cutoff frequency of the identified plant model;
Means for presetting the property of the fuel property estimate with respect to the cutoff frequency;
Means for calculating a fuel property estimated value by retrieving this characteristic from the calculated cutoff frequency;
Means for calculating the fuel supply amount based on the estimated fuel property value;
Means for determining whether the region where the exhaust air-fuel ratio fluctuates due to a factor other than the fuel property is any one of the following states 1 to 15 ;
State 1: The fuel vapor that evaporates in the fuel tank is guided to the canister and adsorbed on the activated carbon in the canister, the purge valve is opened under the purge ON condition, the suction negative pressure developed downstream of the throttle valve , and the canister Purging when equipped with a device that uses fresh air from the air introduction path to separate the fuel vapor adsorbed on the activated carbon and introduce it into the intake pipe
State 2: The fuel vapor that evaporates in the fuel tank is guided to the canister and adsorbed to the activated carbon in the canister, the purge valve is opened when the predetermined operating condition is reached, the suction negative pressure developed downstream of the throttle valve , and the canister When equipped with a device that uses fresh air from the installed air introduction path to release the fuel vapor adsorbed on the activated carbon and introduces it into the intake pipe , the purge period is prohibited and the delay period is longer than the purge is prohibited. It has not passed
Condition 3: if with a brake booster that utilizes negative pressure to develop in the downstream throttle valve, an ON time of the brake switch
Condition 4: when equipped with a brake booster that utilizes negative pressure to develop in the downstream throttle valve, OFF time and a brake switch of the brake switch is in a state that has not elapsed Delay period more turned OFF
Condition 5: when the cylinders distribution unstable region has a predetermined number of rotation and the load of the engine as parameters, is the cylinder distribution unstable region
Condition 6: When the cylinders distribution unstable region has a predetermined number of rotation and the load of the engine as a parameter, has not elapsed more de Irei period turned it and cylinder dispensing stable region in the cylinder partitioned stable range condition Is
State 7: When a misfire determination function is provided, it is a misfire determination time.
State 8: When the misfire determination function is provided, the delay period has not elapsed since the misfire determination is canceled and the misfire determination is canceled.
State 9: When EGR device is provided, EGR is in progress
Condition 10: a case of providing the EGR device is in a state of Delay period more banned and EGR in EGR prohibition has not elapsed
Condition 11: a case of providing the swirl control valve is in a state that has not passed more delay periods to the swirl control valves in a closed state or an open state
State 12: When an automatic transmission with a lock-up mechanism is in the non-lockup
State 13: In a state where an automatic transmission with a lock-up mechanism is provided, the delay period has not elapsed since the lock-up and the lock-up.
State 14: When a fuel cut function is provided, the fuel is being cut
Condition 15: a case of providing a fuel cut function, area delay period from and fuel Kattorika bar not in a fuel cut is in the state not elapsed exhaust air-fuel ratio by a factor other than the fuel property from the result of this determination is to change the A fuel supply control device for an engine, comprising: means for prohibiting sampling of the input / output data in any one of states 1 to 15 . The engine fuel supply control device according to claim 9 or 10 , wherein the estimation result of the fuel property is stored in a nonvolatile memory. 12. The engine fuel supply control device according to claim 11 , wherein the estimated fuel property value is stored in a nonvolatile memory. The estimation of the fuel property is lighter than the reference fuel when the identified model model has a cutoff frequency higher than the cutoff frequency of the reference model when the reference model is matched with the reference fuel. The engine fuel supply control device according to claim 9 , wherein the fuel supply control device is an estimation. The estimation of the fuel property is such that, when the reference model is matched with a reference fuel, a difference between the cut-off frequency of the identified plant model and the cut-off frequency of the reference model is outside an allowable range, and the plant model 11. The engine fuel supply control device according to claim 10 , wherein when the cut-off frequency is higher than the cut-off frequency of the reference model, it is estimated that the fuel is lighter than the reference fuel. The adjustment according to any one of claims 9 , 10 , 11 , 13 , 14 , and 15 , wherein the adjustment to reduce the prediction error is to adjust the prediction error to a minimum. The fuel supply control device for the engine described.

Images